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89-423: COSMAC may refer to: The RCA (CDP)1802 microprocessor, aka RCA COSMAC The COSMAC ELF an RCA COSMAC microprocessor–based computer released 1976, sold as a kit The COSMAC VIP an RCA COSMAC microprocessor–based computer aimed at video games, released 1977, sold as a kit See also [ edit ] CosMc's , a spin-off of McDonald's Topics referred to by

178-462: A "low" and between 2.4 V and V CC for a "high", providing at least 0.4 V of noise immunity . Standardization of the TTL levels is so ubiquitous that complex circuit boards often contain TTL chips made by many different manufacturers selected for availability and cost, compatibility being assured. Two circuit board units off the same assembly line on different successive days or weeks might have

267-432: A different mix of brands of chips in the same positions on the board; repair is possible with chips manufactured years later than original components. Within usefully broad limits, logic gates can be treated as ideal Boolean devices without concern for electrical limitations. The 0.4 V noise margins are adequate because of the low output impedance of the driver stage, that is, a large amount of noise power superimposed on

356-406: A few hundred transistors each. Functions within a single package generally range from a few logic gates to a microprocessor bit-slice . TTL also became important because its low cost made digital techniques economically practical for tasks previously done by analog methods. The Kenbak-1 , ancestor of the first personal computers , used TTL for its CPU instead of a microprocessor chip, which

445-420: A form of surface-mount package, with leads suitable for welding or soldering to printed circuit boards. Today , many TTL-compatible devices are available in surface-mount packages, which are available in a wider array of types than through-hole packages. TTL is particularly well suited to bipolar integrated circuits because additional inputs to a gate merely required additional emitters on a shared base region of

534-574: A go-between, using multiple instructions to perform the operations. The processor has five special I/O lines. There is a single Q output that can be set with the SEQ instruction and reset with the REQ instruction. There are four external, single-bit flag inputs, EF1, EF2, EF3, and EF4, and there are eight dedicated branch instructions to conditionally branch based on the state of those input lines. There are seven Input and seven Output port instructions that utilize

623-635: A greatly simplified single-board system known as then COSMAC ELF . Building instructions were described in an article in Popular Electronics magazine in 1976, and an expanded version with various upgrades in a second article in 1977. A unique feature of the ELF is that it did not require any read only memory (ROM) for startup, instead, the processor's direct memory access (DMA) system was used to read front-panel switches directly into memory. RCA debated whether to introduce pre-packaged versions of

712-688: A single-chip implementation immediately. Jerry Herzog led the design of the single-chip version, which sampled in 1975 and entered production in 1976. In contrast to most designs of the era, which were fabricated using the NMOS process, the COSMAC was implemented in CMOS form and used static logic . This allowed it to run at lower power settings and even be stopped completely; in addition it would run cooler and not generate as much heat as NMOS chips. RCA also produced radiation hardened versions, which found use in

801-596: A stack. Although any of the available registers can be used for this technique, per programmer's preference, many use the routine supplied by RCA in the CDP1802 User Manual, where the suggested register usage is R2 = Stack Pointer, R3 = General Program Counter (PC), R4 = Call, R5 = Return, R6 = Passed Arguments Pointer (non-destructive). Even though these supportive routines are small, there is an execution speed overhead using them. (as opposed to what would be incurred if actual CALL and RET instructions were part of

890-420: A standard TTL input while not allowing the voltage to rise to more than 0.4 volts. The output stage of the most common TTL gates is specified to function correctly when driving up to 10 standard input stages (a fanout of 10). TTL inputs are sometimes simply left floating to provide a logical "1", though this usage is not recommended. Standard TTL circuits operate with a 5- volt power supply. A TTL input signal

979-508: A subroutine returns, it jumps to the location immediately preceding its entry point so that after the SEP "return" instruction returns control to the caller, the register will be pointing to the right value for next usage. (the processor always increments the PC after reference and usage (retrieving the next instruction to execute), so this technique works as noted) An interesting variation of this scheme

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1068-623: A volume control was implemented). Traditionally, the EF4 line is attached to the INPUT momentary pushbutton on the COSMAC Elf. Other systems might use one of the other lines. There are some other special use registers and flags, some internal, and some usable programmatically: 4-bit N, P, X, and I; 8-bit T; and 1-bit IE. On the Internet, there is many versions of a Table of the 1802 Instructions, here

1157-697: A wide range of logic gates , flip-flops , counters, and other circuits. Variations of the original TTL circuit design offered higher speed or lower power dissipation to allow design optimization. TTL devices were originally made in ceramic and plastic dual in-line package (s) and in flat-pack form. Some TTL chips are now also made in surface-mount technology packages. TTL became the foundation of computers and other digital electronics. Even after Very-Large-Scale Integration (VLSI) CMOS integrated circuit microprocessors made multiple-chip processors obsolete, TTL devices still found extensive use as glue logic interfacing between more densely integrated components. TTL

1246-763: A year of discussion, the company eventually decided to release two mass-market products based on the platform, a kit computer known as the COSMAC VIP , and a game console known as the RCA Studio II . The machines had been available since 1975, but the Studio II was announced only in January 1977, a couple of months after the Fairchild Channel F became the first cartridge-based machine on the market. Both would soon be eclipsed and largely forgotten due to

1335-501: Is a common debug interface for embedded devices. Handheld devices such as graphing calculators and NMEA 0183 -compliant GPS receivers and fishfinders also commonly use UART with TTL. TTL serial is only a de facto standard: there are no strict electrical guidelines. Driver–receiver modules interface between TTL and longer-range serial standards: one example is the MAX232 , which converts from and to RS-232 . Differential TTL

1424-504: Is applied to many successive generations of bipolar logic, with gradual improvements in speed and power consumption over about two decades. The most recently introduced family 74Fxx is still sold today (as of 2019), and was widely used into the late 90s. 74AS/ALS Advanced Schottky was introduced in 1985. As of 2008, Texas Instruments continues to supply the more general-purpose chips in numerous obsolete technology families, albeit at increased prices. Typically, TTL chips integrate no more than

1513-406: Is buffered by a common emitter amplifier. Inputs both logical ones. When all the inputs are held at high voltage, the base–emitter junctions of the multiple-emitter transistor are reverse-biased. Unlike DTL, a small “collector” current (approximately 10 μA) is drawn by each of the inputs. This is because the transistor is in reverse-active mode . An approximately constant current flows from

1602-515: Is defined as "low" when between 0 V and 0.8 V with respect to the ground terminal, and "high" when between 2 V and V CC (5 V), and if a voltage signal ranging between 0.8 V and 2.0 V is sent into the input of a TTL gate, there is no certain response from the gate and therefore it is considered "uncertain" (precise logic levels vary slightly between sub-types and by temperature). TTL outputs are typically restricted to narrower limits of between 0.0 V and 0.4 V for

1691-405: Is different from Wikidata All article disambiguation pages All disambiguation pages RCA 1802 The processor design traces its history to an experimental home computer designed by Joseph Weisbecker in the early 1970s, built at his home using TTL components. RCA began development of the CMOS version of the processor design in 1973, sampling it in 1974 with plans to move to

1780-569: Is done on a piece of paper. Of course sometimes the Data is moved to and from the Ram Memory section, and different Branches of the Program are done, as needed, in the flow of time. There are three types of unconditional and conditional branching in the 1802, Short and Long, and Skips. Short branches are 2-byte instructions, and use 256-byte range, single byte address, page absolute addressing in

1869-581: Is one link : https://www.atarimagazines.com/computeii/issue3/page52.php There is a number of Tables in the File area for logged in members of the 1802 online club for forum at https://groups.io/g/cosmacelf/files . Each Instruction is a single Byte, of 8 Bits. The 4 Bits to the Left, sometimes called High Order Hex Digit, are to do with the actual nature of the Instruction, and those 4 Bits are involved with

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1958-481: Is substantially slower. Designers can combine ECL and TTL devices in the same system to achieve best overall performance and economy, but level-shifting devices are required between the two logic families. TTL is less sensitive to damage from electrostatic discharge than early CMOS devices. Due to the output structure of TTL devices, the output impedance is asymmetrical between the high and low state, making them unsuitable for driving transmission lines. This drawback

2047-514: Is the 8-bit 'D' register (Data register). The single bit carry flag is DF (Data Flag). Most operations use the D register, including arithmetic and logic functions, and memory referencing load and store instructions. Most 16-bit operations have to work on the lower byte and then the upper byte, via D, using the DF as carry and borrow as needed. An important feature of the 1802 is a set of sixteen registers of 16 bits each, used primarily for addressing. Using

2136-528: Is to have two or more subroutines in a ring so that they are called in round robin order. On early hobbyist computers, tricks and techniques like this were commonly used in the horizontal refresh interrupt to reprogram the scan line address to repeat each scan line four times for the video controller. One well-known and often-used routine is known as SCRT (Standard CALL and RETURN Technique), which allows general purpose subroutine Call and Return, including passing of parameters "in line", and nested subroutines using

2225-400: Is usually overcome by buffering the outputs with special line-driver devices where signals need to be sent through cables. ECL, by virtue of its symmetric low-impedance output structure, does not have this drawback. The TTL "totem-pole" output structure often has a momentary overlap when both the upper and lower transistors are conducting, resulting in a substantial pulse of current drawn from

2314-553: The CyberVision 2001 systems sold through Montgomery Ward in the late 1970s, as well as the RCA Studio II video game console (one of the first consoles to use bitmapped graphics). The Edukit single-board computer trainer system, similar to an expanded COSMAC Elf , was offered by Modus Systems Ltd. in Britain in the early 1980s. Infinite Incorporated produced an 1802-based, S-100 bus expandable console computer trainer in

2403-514: The DEC VAX and Data General Eclipse ; however some computer families were based on proprietary components (e.g. Fairchild CTL) while supercomputers and high-end mainframes used emitter-coupled logic . They were also used for equipment such as machine tool numerical controls, printers and video display terminals, and as microprocessors became more functional for "glue logic" applications, such as address decoders and bus drivers, which tie together

2492-454: The DMA auto-boot loader functionality. There are also some minor pin function changes, but the line continues to be produced in its original 40-pin dual in-line package (DIP) format. Joseph Weisbecker had long been fascinated with the potential for computers in the home, having stated as early as 1955 that he expected they would one day be built into practically every device. The technology of

2581-438: The "totem-pole" output stage is the decreased voltage level (no more than 3.5 V) of the output logical "1" (even if the output is unloaded). The reasons for this reduction are the voltage drops across the V 3 base–emitter and V 5 anode–cathode junctions. Like DTL, TTL is a current-sinking logic since a current must be drawn from inputs to bring them to a logic 0 voltage level. The driving stage must absorb up to 1.6 mA from

2670-422: The 16 registers; however, the called subroutine must know (hard coded) what the calling PC register is to perform the "return" instruction. The SEP instruction is used to call a subroutine pointed to by one of the 16-bit registers and another SEP to return to the caller (SEP stands for Set Program Counter , and selects which one of the 16 registers is to be used as the program counter from that point onward). Before

2759-612: The 1802 in their second-generation Electronic Lean-Burn System, with electronic spark control, one of the first on-board auto computer-based control systems. The 1802 was used in the manufacture of many pinball machines and video arcade games in Spain. A high-speed version of the 1802 was fabricated in Silicon on Sapphire (SOS) semiconductor process technology, which gives it a degree of resistance to radiation and electrostatic discharge (ESD). A different radiation-hardened version of

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2848-402: The 1802, developed jointly by RCA and Sandia National Laboratories , was built on bulk silicon using C L (Closed COS/MOS Logic) technology. Along with its extreme low-power abilities, this makes the chip well-suited in space and military applications. (Also, at the time the 1802 was introduced, very few, if any, other radiation-hardened microprocessors were available in the market). The 1802

2937-696: The 1980s and 1990s used the 1802, amongst them: The first high-level language available for the 1802 was Forth , provided by Forth, Inc. and it was known as MicroFORTH, in 1976 (see Forth Inc's archive). Other available programming languages, both interpreters and compilers, are CHIP-8 (It was also invented by Joseph Weisbecker ) (and variants), 8th (a version of Forth created by Lee Hart), Tom Pittman's Tiny BASIC , C, various Assemblers and cross-assemblers, and others. Other specialty languages were used by federal agencies such as NASA and its installations, including Johnson Space Center, AMES, Goddard, Langley, Marshall, and Jet Propulsion Laboratory (JPL), which included

3026-406: The 1990s. Until the advent of programmable logic , discrete bipolar logic was used to prototype and emulate microarchitectures under development. TTL inputs are the emitters of bipolar transistors. In the case of NAND inputs, the inputs are the emitters of multiple-emitter transistors , functionally equivalent to multiple transistors where the bases and collectors are tied together. The output

3115-404: The 7401 and 7403 series. Open-collector outputs of some gates have a higher maximum voltage, such as 15 V for the 7426, useful when driving non-TTL loads. To solve the problem with the high output resistance of the simple output stage the second schematic adds to this a "totem-pole" (" push–pull ") output. It consists of the two n-p-n transistors V 3 and V 4 , the "lifting" diode V 5 and

3204-491: The ELF to the market. While they debated, further development led to a simplified machine combining the ELF with a new display driver chip, the CDP1861 , to produce a game console . During this time, Joyce was hired by RCA to write several videogames for the platform, including a quiz-style educational product in partnership with Random House , one of the many companies that had been picked up by RCA's buying sprees. After

3293-541: The Eastern Bloc (Soviet Union, GDR, Poland, Czechoslovakia, Hungary, Romania — for details see 7400 series ). Not only did others make compatible TTL parts, but compatible parts were made using many other circuit technologies as well. At least one manufacturer, IBM , produced non-compatible TTL circuits for its own use; IBM used the technology in the IBM System/38 , IBM 4300 , and IBM 3081 . The term "TTL"

3382-578: The HAL/S cross-compiler, STOIC , a Forth-like language, and others. Interpreter for Process Structures (IPS), a programming language and development environment, was specifically written and used for real-time control of AMSAT satellites. The 1802 chip and computers using the microprocessor have been emulated and simulated in hardware and/or software by hobbyists. There are three designs in VHDL for an FPGA . A bus-accurate, full speed COSMAC Elf clone

3471-585: The I Register. The 4 Bits to the Right, sometimes called Low Order Hex Digit, are to do with the working Register, where Data is taken from, or put into it, and those 4 Bits are involved with the N Register. When a Program is being done, the various stages of the work and the Processes, are stored temporarily in the Register pointed to by the N Register, like what happens, when long Multiplication, or long Division,

3560-447: The RX register and D accumulator. The EF and Q lines were typically used for multiple interfaces on 1802-based hobbyist computers because of the lines' favorable and easy handling. It was typical for the Q line to drive a status LED , a cassette interface, an RS-232 interface, and the speaker. This meant that the user could actually hear RS-232 and cassette data being transmitted (unless

3649-458: The SEP instruction, you can select any of the 16 registers to be the program counter ; using the SEX instruction, you can select any of the 16-bit registers to be the index register . Register R0 has the special use of holding the memory address for the built-in DMA controller. Register R1 has the special use of being the program counter for the interrupt handler. There are instructions that allow

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3738-399: The address into a spare register; followed by an instruction to select that register as the index register; followed, finally, by the intended operation on the data variable that is pointed to by that address. Transistor-transistor logic Transistor–transistor logic ( TTL ) is a logic family built from bipolar junction transistors . Its name signifies that transistors perform both

3827-498: The aerospace field. These remain in production as of 2022, and as of 2008 continued to be produced by Renesas (formerly Intersil ). Successors to the 1802 are the CDP1804, CDP1805, and CDP1806, which have an extended instruction set, other enhanced features (like on-chip RAM and ROM, and built-in timer), with some versions running at faster clock speeds, though not a significant speed difference. Some features are also lost, like

3916-452: The bottom of the resistor and ground. If one input voltage becomes zero, the corresponding base–emitter junction of the multiple-emitter transistor is in parallel with these two junctions. A phenomenon called current steering means that when two voltage-stable elements with different threshold voltages are connected in parallel, the current flows through the path with the smaller threshold voltage. That is, current flows out of this input and into

4005-418: The company's recent sale of their mainframe computer business to Sperry Rand with a huge writedown . Eventually, the company became interested in the system and began adapting it to their newly introduced COS/MOS fabrication system. A 1973 lab report refers to a "prototype" being delivered in 1972, but this is likely referring to the original TTL implementation. It goes on to note that an effort to reduce

4094-417: The constant, each one followed by a Put instruction to the register, PHI and PLO). The two addressing modes Indirect register , and Indirect register with auto-increment are then fairly efficient, to perform 8-bit operations on the data in the accumulator. There are no other addressing modes, though. Thus, the direct addressing mode needs to be emulated using the four instructions mentioned earlier to load

4183-508: The contents of one register to another involves four instructions (one Get and one Put on the HI byte of the register, and a similar pair for the LO byte: GHI R1; PHI R2; GLO R1; PLO R2). Similarly, loading a new constant into a register (such as a new address for a subroutine jump, or the address of a data variable) also involves four instructions (two load immediate, LDI, instructions, one for each half of

4272-628: The controls of the Phoenix missile . TTL became popular with electronic systems designers after Texas Instruments introduced the 5400 series of ICs, with military temperature range, in 1964 and the later 7400 series , specified over a narrower range and with inexpensive plastic packages, in 1966. The Texas Instruments 7400 family became an industry standard. Compatible parts were made by Motorola , AMD , Fairchild , Intel , Intersil , Signetics , Mullard , Siemens , SGS-Thomson , Rifa , National Semiconductor , and many other companies, even in

4361-424: The current-limiting resistor R 3 (see the figure on the right). It is driven by applying the same current steering idea as above. When V 2 is "off", V 4 is "off" as well and V 3 operates in active region as a voltage follower producing high output voltage (logical "1"). When V 2 is "on", it activates V 4 , driving low voltage (logical "0") to the output. Again there is a current-steering effect:

4450-547: The design of a small machine using RCA transistor-transistor logic (TTL) ICs to construct the processor. Other parts, switches and lamps and such, he had to buy from Radio Shack , deliberately spreading his purchases around four stores so no one would ask him why he was buying so many parts. The design was running in October 1971, containing 100 chips spread over multiple circuit boards . The result, which he called FRED, ostensibly for Flexible Recreational Educational Device,

4539-450: The development of the COSMAC in the early 1970s, it was some time before they introduced their own products based on it. In 1975, a prototype of an arcade game machine with swappable ROMs was experimented with for the coin-op business, but was ultimately abandoned. Meanwhile, Weisbecker had adapted the original FRED, known within RCA as System 00 by this time, using the new chipset to produce

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4628-436: The digital domain but would not ordinarily be used where analog amplification is the primary purpose. TTL inverters can also be used in crystal oscillators where their analog amplification ability is significant. A TTL gate may operate inadvertently as an analog amplifier if the input is connected to a slowly changing input signal that traverses the unspecified region from 0.8 V to 2 V. The output can be erratic when

4717-784: The diode. However, this technique actually converts the sophisticated "totem-pole" output into a simple output stage having significant output resistance when driving a high level (determined by the external resistor). Like most integrated circuits of the period 1963–1990, commercial TTL devices are usually packaged in dual in-line packages (DIPs), usually with 14 to 24 pins, for through-hole or socket mounting. Epoxy plastic (PDIP) packages were often used for commercial temperature range components, while ceramic packages (CDIP) were used for military temperature range parts. Beam-lead chip dies without packages were made for assembly into larger arrays as hybrid integrated circuits. Parts for military and aerospace applications were packaged in flatpacks ,

4806-686: The embedded market, because its CMOS design allowed it to work at lower power. By the late 1970s it was widely used in many industrial settings, and especially aerospace. Multiple 1802s were used as auxiliary IO processors in the Galileo probe to Jupiter in 1989, and it remains in use in similar roles to this day. A number of early microcomputers were based on the 1802, including the COSMAC ELF (1976), Netronics ELF II , Quest SuperELF , COSMAC VIP , Comx-35 , Finnish Telmac 1800 , Telmac TMC-600 and Oscom Nano , Yugoslav Pecom 32 and 64 , and

4895-414: The equivalent TTL component and with the same pinouts . For example, the 74HCT00 series provides many drop-in replacements for bipolar 7400 series parts, but uses CMOS technology. Successive generations of technology produced compatible parts with improved power consumption or switching speed, or both. Although vendors uniformly marketed these various product lines as TTL with Schottky diodes , some of

4984-523: The era made small embedded computers impossible, but the introduction of the integrated circuit (IC) in the 1960s changed things dramatically. In 1974 he described the possibilities in an IEEE Computer article: For 20 years computer hardware has become increasingly complex, languages more devious, and operating systems less efficient. Now, microcomputers afford some of us the opportunity to return to simpler systems. Inexpensive…microcomputers could open up vast new markets. Beginning in 1970, Weisbecker began

5073-509: The era were invariably aimed at the embedded processor space, and those that had been designed for computer use were generally more complex systems, and often 16-bit. Although the COSMAC had been designed for computer use, RCA's slow market entry and undersupported attempts in this market ultimately failed and other processors like the MOS 6502 and Zilog Z80 would come to dominate this market. Ironically, COSMAC would ultimately find great success in

5162-501: The function blocks realized in VLSI elements. The Gigatron TTL is a more recent (2018) example of a processor built entirely with TTL integrated circuits. While originally designed to handle logic-level digital signals, a TTL inverter can be biased as an analog amplifier. Connecting a resistor between the output and the input biases the TTL element as a negative feedback amplifier . Such amplifiers may be useful to convert analog signals to

5251-505: The input is in this range. A slowly changing input like this can also cause excess power dissipation in the output circuit. If such an analog input must be used, there are specialized TTL parts with Schmitt trigger inputs available that will reliably convert the analog input to a digital value, effectively operating as a one bit A to D converter. TTL serial refers to single-ended serial communication using raw transistor voltage levels: "low" for 0 and "high" for 1. UART over TTL serial

5340-685: The input transistor. If individually packaged transistors were used, the cost of all the transistors would discourage one from using such an input structure. But in an integrated circuit, the additional emitters for extra gate inputs add only a small area. At least one computer manufacturer, IBM, built its own flip chip integrated circuits with TTL; these chips were mounted on ceramic multi-chip modules. TTL devices consume substantially more power than equivalent CMOS devices at rest, but power consumption does not increase with clock speed as rapidly as for CMOS devices. Compared to contemporary ECL circuits, TTL uses less power and has easier design rules but

5429-632: The instructions took 16 or 24 clock cycles to complete, the 1802 was not particularly fast. For comparison, the 6502 completes most instruction in 2 to 4 clock cycles, with the longest (official instruction) taking 7 cycles. Various suffixes to the CDP1802 part number denote technical specifications, including (A, B, & C) operating speed (3.2 MHz to 6.4 MHz), temperature (-40 °C to +85 °C, -55 °C to +125 °C), and voltage ranges (4V to 10.5V), package type (D, E, Q), and burn-in (X). These were somewhat standardized between

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5518-698: The late 1970s called the UC1800, available assembled or in kit form. As part of 1802 retrocomputing hobbyist work, other computers have been built more recently (post-2000), including the Membership Card microcomputer kit that fits in an Altoids tin and the Spare Time Gizmos Elf 2000 (Elf 2K), among others. See § Emulators and simulators for other systems. The 1802 was also used in scientific instruments and commercial products. Post-1980 Chrysler and associated model vehicles use

5607-648: The logic function (the first "transistor") and the amplifying function (the second "transistor"), as opposed to earlier resistor–transistor logic (RTL) and diode–transistor logic (DTL). TTL integrated circuits (ICs) were widely used in applications such as computers , industrial controls, test equipment and instrumentation, consumer electronics, and synthesizers . After their introduction in integrated circuit form in 1963 by Sylvania Electric Products , TTL integrated circuits were manufactured by several semiconductor companies. The 7400 series by Texas Instruments became particularly popular. TTL manufacturers offered

5696-641: The microprocessor without affecting its operation. It has two separate 8-pin buses: an 8-bit bidirectional data bus and a time-multiplexed address bus , with the high-order and low-order 8-bits of the 16-bit address being accessed on alternate clock cycles. This contrasts with most designs of the era, like the MOS 6502 and Intel 8080 , which used a 16-bit address bus. The 1802 has a single bit , programmable and testable output port (Q), and four input pins that are directly tested by branch instructions (EF1-EF4). These pins allow simple input/output (I/O) tasks to be handled directly and easily programmed. Because

5785-406: The microprocessor's design) This setup allows R0 to be used for DMA and R1 to be used for Interrupts, if desired, allowing R7 through RF (hex) for general program usage. Because of the 16-bit address bus, and the 8-bit data bus, the sixteen general purpose registers are 16 bits wide, but the accumulator D-register is only 8 bits wide. The accumulator, therefore, tends to be a bottleneck. Transferring

5874-513: The military-specification temperature range of −55 to +125 °C. Special quality levels and high-reliability parts are available for military and aerospace applications. Radiation-hardened devices (for example from the SNJ54 series) are offered for space applications. Before the advent of VLSI devices, TTL integrated circuits were a standard method of construction for the processors of minicomputer and midrange mainframe computers, such as

5963-464: The output is needed to drive an input into an undefined region. In some cases (e.g., when the output of a TTL logic gate needs to be used for driving the input of a CMOS gate), the voltage level of the "totem-pole" output stage at output logical "1" can be increased closer to V CC by connecting an external resistor between the V4 collector and the positive rail. It pulls up the V 5 cathode and cuts-off

6052-449: The output is not loaded. A common variation omits the collector resistor of the output transistor, making an open-collector output. This allows the designer to fabricate wired logic by connecting the open-collector outputs of several logic gates together and providing a single external pull-up resistor . If any of the logic gates becomes logic low (transistor conducting), the combined output will be low. Examples of this type of gate are

6141-423: The output stage. The main advantage of TTL with a "totem-pole" output stage is the low output resistance at output logical "1". It is determined by the upper output transistor V 3 operating in active region as an emitter follower . The resistor R 3 does not increase the output resistance since it is connected in the V 3 collector and its influence is compensated by the negative feedback. A disadvantage of

6230-425: The positive rail, through the resistor and into the base of the multiple emitter transistor. This current passes through the base–emitter junction of the output transistor, allowing it to conduct and pulling the output voltage low (logical zero). An input logical zero. Note that the base–collector junction of the multiple-emitter transistor and the base–emitter junction of the output transistor are in series between

6319-510: The power supply. These pulses can couple in unexpected ways between multiple integrated circuit packages, resulting in reduced noise margin and lower performance. TTL systems usually have a decoupling capacitor for every one or two IC packages, so that a current pulse from one TTL chip does not momentarily reduce the supply voltage to another. Since the mid 1980s, several manufacturers supply CMOS logic equivalents with TTL-compatible input and output levels, usually bearing part numbers similar to

6408-510: The processor to a two-chip implementation with deliveries in COS/MOS in 1974. It is here that the processor is first referred to as COSMAC, for COmplementary-Symmetry-Monolithic-Array Computer. It goes on to state that another lab will be producing the system in an 8-chip silicon-on-sapphire format, although the date is simply "soon after" the CMOS versions, and that plans for a single-chip version were already being planned. Although RCA began

6497-906: The range 0 to 255 (hex FF). There is no relative branching. The short branch always jumps within the page that contains the address byte. Long branches use full 16-bit addressing to support the 64K memory address space, and are the only 3-byte instructions. Skip instructions increment the PC by one for the unconditional Short Skip, or two for the Long Skips. Only the Long Skip has conditional branching. The processor does not have standard subroutine CALL address and RET instructions, though they can be simulated. The 16-register design makes possible some interesting subroutine call and return mechanisms, though they are better suited to small programs than general purpose coding. A few commonly used subroutines can be called quickly by keeping their address in one of

6586-675: The release of the Atari 2600 later that year. RCA canceled the Studio II in February 1978. RCA also released a series of modular computer systems, based on the RCA Microboard form factor from the 1802's initial release, up until the collapse of RCA itself. These were mainly aimed at industrial applications and systems development, and were highly configurable. The COSMAC was unique among early 8-bit processors in that it had been explicitly designed for microcomputer use; other designs of

6675-417: The resistor R 3 limits the current flowing directly through the series connected transistor V 3 , diode V 5 and transistor V 4 that are all conducting. It also limits the output current in the case of output logical "1" and short connection to the ground. The strength of the gate may be increased without proportionally affecting the power consumption by removing the pull-up and pull-down resistors from

6764-409: The same term [REDACTED] This disambiguation page lists articles associated with the title COSMAC . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=COSMAC&oldid=1189138251 " Category : Disambiguation pages Hidden categories: Short description

6853-405: The series combination of V 2 's C-E junction and V 4 's B-E junction is in parallel with the series of V 3 B-E, V 5 's anode-cathode junction, and V 4 C-E. The second series combination has the higher threshold voltage, so no current flows through it, i.e. V 3 base current is deprived. Transistor V 3 turns "off" and it does not impact on the output. In the middle of the transition,

6942-408: The system and began writing programs for it. This included several games, which were ported to later machines based on the COSMAC. When RCA entered the game console business in the later 1970s, these games were burned to ROM cartridge form, and Joyce became the first known female commercial videogame developer. Weisbecker demonstrated the machine to RCA management throughout this period, but there

7031-414: The transition over a diode input structure. The main disadvantage of TTL with a simple output stage is the relatively high output resistance at output logical "1" that is completely determined by the output collector resistor. It limits the number of inputs that can be connected (the fanout ). Some advantage of the simple output stage is the high voltage level (up to V CC ) of the output logical "1" when

7120-559: The underlying circuits, such as used in the LS family, could rather be considered DTL . Variations of and successors to the basic TTL family, which has a typical gate propagation delay of 10ns and a power dissipation of 10 mW per gate, for a power–delay product (PDP) or switching energy of about 100 pJ , include: Most manufacturers offer commercial and extended temperature ranges: for example Texas Instruments 7400 series parts are rated from 0 to 70 °C, and 5400 series devices over

7209-410: The values in these registers to be set and read via D, separately working the upper and lower 8-bits at a time. There are also instructions to perform increment and decrement of the entire 16-bit value, and a few instructions perform automatic increment and decrement, like LDA (load advance) and STXD (store via X and decrement). 16-bit register and value comparisons would also need to use the D register as

7298-580: The various source suppliers, including RCA, Intersil, Harris, Hughes Aircraft, and Solid State Scientific (SSS). Hughes used the HCMP prefix, and SSS used the SCP (and possibly BCP) prefix, instead of CDP, and had additional suffixes that have not been documented as of yet. (examples: CDP1802A, CDP1802ACE, CDP1802BCD, HCMP1802AP, SCP1802D) The 1802 is an 8-bit byte machine, with minimal support for 16-bit operations, except via 2-byte manipulation. The primary accumulator

7387-430: The zero (low) voltage source. As a result, no current flows through the base of the output transistor, causing it to stop conducting and the output voltage becomes high (logical one). During the transition the input transistor is briefly in its active region; so it draws a large current away from the base of the output transistor and thus quickly discharges its base. This is a critical advantage of TTL over DTL that speeds up

7476-475: Was created without a CDP1802 microprocessor chip or CDP1861 video chip using PIC microcontrollers . An online simulator of the COSMAC Elf (enhanced) written in JavaScript runs in the user's browser with no need to download. The RCA 1802 has a static core CMOS design with no minimum clock frequency , so that it can be run at very low speeds and low power, including a clock frequency of zero to suspend

7565-506: Was invented in 1961 by James L. Buie of TRW , which declared it "particularly suited to the newly developing integrated circuit design technology." The original name for TTL was transistor-coupled transistor logic (TCTL). The first commercial integrated-circuit TTL devices were manufactured by Sylvania in 1963, called the Sylvania Universal High-Level Logic family (SUHL). The Sylvania parts were used in

7654-456: Was little interest at first. This was shortly after David Sarnoff had retired and handed the CEO role to his son, Robert Sarnoff . Robert was more interested in building the media side of the company while dating recording stars, ignoring RCA Laboratories in spite of a number of industry-leading developments taking place there. Some of the skepticism displayed by management may have had to do with

7743-451: Was not available in 1971. The Datapoint 2200 from 1970 used TTL components for its CPU and was the basis for the 8008 and later the x86 instruction set. The 1973 Xerox Alto and 1981 Star workstations, which introduced the graphical user interface , used TTL circuits integrated at the level of arithmetic logic units (ALUs) and bitslices, respectively. Most computers used TTL-compatible " glue logic " between larger chips well into

7832-470: Was packaged into a box that was not unlike the Altair 8800 of a few years later, with toggle switches on the front panel for input, lamps for output, and later adding a hex pad keyboard. Weisbecker added new features continually and by 1972 it had gained a character generator and the ability to load and save programs on cassette tapes . Weisbecker's daughter, Joyce Weisbecker , was immediately drawn to

7921-583: Was used in many spacecraft and space science programs, experiments, projects and modules such as the Galileo spacecraft , Magellan , the Plasma Wave Analyzer instrument on ESA's Ulysses spacecraft, various Earth-orbiting satellites and satellites carrying amateur radio. The 1802 has also been verified from NASA source documentation to have been used in the Hubble Space Telescope . A number of British military items from

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