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42-818: The data rate was nominally 600 bit/s, but the simple error correction and short gaps between the resulting packets lowered this somewhat. In the end, its rate was roughly double that of the formats used by the Commodore Datasette or the TI-99/4 . In some markets, where the Program Recorder was the only cost-effective storage solution, software-based high-performance modes were developed that operated more than three times as fast, and as much as four times as fast with simple hardware modifications. The drives had several features not commonly found on other platforms. The system's device driver supported

84-428: A daisy chain is a wiring scheme in which multiple devices are wired together in sequence or in a ring, similar to a garland of daisy flowers . Daisy chains may be used for power, analog signals, digital data, or a combination thereof. The term daisy chain may refer either to large scale devices connected in series, such as a series of power strips plugged into each other to form a single long line of strips, or to

126-456: A network packet is a formatted unit of data carried by a packet-switched network . A packet consists of control information and user data; the latter is also known as the payload . Control information provides data for delivering the payload (e.g., source and destination network addresses , error detection codes, or sequencing information). Typically, control information is found in packet headers and trailers . In packet switching ,

168-546: A Chelco mechanism and another using Sanyo . They can be distinguished by the colored sticker inside the drive bay, Chelco used silver while Sanyo was orange. When the XE series were released they were initially sold into existing markets and Atari introduced a number of XE-styled accessories to go with them. This led to the introduction of the XC11 in the UK around 1986, which are essentially

210-413: A computing system in a daisy chain configuration by connecting each component to another similar component, rather than directly to the computing system that uses the component. Only the last component in the chain directly connects to the computing system. For example, chaining multiple components that each have a UART port to each other. The components must also behave cooperatively. e.g., only one seizes

252-474: A number of interfaces that allowed any third party cassette deck to be used. The Atari 8-bit computers featured an advanced (for the era) input/output system, Atari SIO . Devices normally had in and out ports that allowed a number of devices to be daisy-chained together into a single port on the host computer. Most devices were "smart", listening for commands being sent through the data stream for instructions pertaining it its own device number. For instance,

294-563: A packet-based format with checksums for error detection, as opposed to lacking any error detection or using whole-file checksums. The driver included separate formats for binary data and more complex data that required longer to process it. The left audio channel could be used to send audio through to the television speaker, which could be used to provide music during the loading period, or in program-controlled computer aided instruction systems. The original 400 and 800 models, released in 1979, were housed in robust beige colored plastic cases and

336-431: A potential entry into the education market, forming an educational arm and producing a series of tapes early in the system's history. Best known among these was States and Capitals , a simple quiz game that became the topic of several of Atari's television ads. The basic signaling rate of the system was 600 bit/s, but there was some additional overhead due to the inter-record gaps and the packet structure. This reduced

378-401: A series of computer peripherals were released to match this design. The original 410 was a modified Sears model 799.21672500 Solid State Cassette Recorder with a Japanese mechanism by Bigston. It was a relatively large unit and was unique among the line in that it featured a metal carrying handle that slid out from the front of the unit, identical to its Sears counterpart. This was replaced by

420-558: A short bit of mark tone, 5327 Hz. The associated program would then turn on the MOTOR line to begin playback and then read data until it saw a series of ones on the POKEY. At this point the program would stop the cassette again and interact with the user. This was typically used to stop and ask multiple-choice questions before proceeding to the next section of audio. Atari saw the CAI market as

462-564: A short note on ways to improve the reliability of reading data from the decks. A fuller treatment appeared in Antic in February 1984. This involved replacing two resistors, one each in both the high and low-frequency filters. This reduces the width of their bell-curve-shaped frequency response and eliminates any overlap where a signal might produce output in both channels. Network packet In telecommunications and computer networking ,

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504-422: A single checksum byte at the end, so the overall packet was 132 bytes long. The first two bytes were 01010101 01010101, used for clock recovery by the POKEY to address tape stretch and other common problems in cassette systems. The next byte, the control byte, specified if the packet had a complete 128 bytes of data, less than that, or was a special end-of-file (EOF) marker. Only the packet immediately preceding

546-566: A single drive. This was enforced by leaving off the daisy-chaining port on the tape decks, forcing it to be the last device on the SIO chain. The exception was the 1010, which included a second port and did allow chaining. The system used frequency-shift keying (FSK) to store data on the tapes. When being used to write data, the POKEY chip was set up with one of its four channels producing 5327 Hz for mark and another to 3995 Hz for space, while

588-459: A somewhat smaller and more rounded unit around 1981 using a new mechanism from Transtek or Chelco Sound in Hong Kong . The release of the 600XL and 800XL in 1983 led to the system being repackaged in a much smaller form, the 1010. The new model used the black/white/silver styling of the new machines and was assigned a number in the new 1000-series device numbers. Two versions were made, one using

630-401: A third channel was set to 600 Hz and used as a clock. Data sent to the cassette device driver toggled which of the two tones was played to DATAOUT while being timed by the clock. Each byte was prefixed by a space bit and postfixed by a mark. Reading was accomplished by two narrowband filters in the drive itself, which produced output when the corresponding tone was heard. During playback,

672-497: Is often carried as the payload inside an Ethernet frame, which has its own header and trailer. Per the end-to-end principle , IP networks do not provide guarantees of delivery, non-duplication, or in-order delivery of packets. However, it is common practice to layer a reliable transport protocol such as Transmission Control Protocol on top of the packet service to provide such protection. The Consultative Committee for Space Data Systems ( CCSDS ) packet telemetry standard defines

714-482: The Atari 810 floppy disk drive included a MOS 6507 that watched for commands being sent to a device number selected using switches on the back of the drive. The cassette drive was intended to be a much lower-cost device and this eliminated the possibility of it being smart. Instead, and in contrast to any other devices used with SIO, the cassette system used several dedicated pins in the SIO port that directly controlled

756-683: The NICAM signal is transmitted on a subcarrier alongside the sound carrier. This means that the FM or AM regular mono sound carrier is left alone for reception by monaural receivers. The NICAM packet (except for the header) is scrambled with a nine-bit pseudo-random bit-generator before transmission. Making the NICAM bitstream look more like white noise is important because this reduces signal patterning on adjacent TV channels. Daisy chain (electrical engineering) In electrical and electronic engineering,

798-430: The bandwidth of the transmission medium is shared between multiple communication sessions, in contrast to circuit switching , in which circuits are preallocated for the duration of one session and data is typically transmitted as a continuous bit stream . In the seven-layer OSI model of computer networking , packet strictly refers to a protocol data unit at layer 3, the network layer . A data unit at layer 2,

840-399: The data link layer , is a frame . In layer 4, the transport layer , the data units are segments and datagrams . Thus, in the example of TCP/IP communication over Ethernet , a TCP segment is carried in one or more IP packets , which are each carried in one or more Ethernet frames . The basis of the packet concept is the postal letter: the header is like the envelope, the payload is

882-565: The EOF could be in the shorter format, with the number of used bytes placed in the byte preceding end-of-packet checksum. Both the short packet and EOF packet were padded out to a full 132 bytes long. Between packets, the system played the mark tone continually, with a short Pre-Record Write Tone and a variable length Post-Record Gap, the two combined known as the InterRecord Gap (IRG). The driver supported two writing modes. In Short IRG mode,

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924-465: The IRG was about 0.25 seconds long. This mode was used for most transfers, leaving just enough time for the computer to calculate the checksum and potentially stop the drive if the checksum failed. The other mode, Normal IRG, played a 3 second gap between packets. This time was selected to ensure that the drive could be stopped and restarted without it having advanced past the next packet. Normal IRG

966-545: The Short IRG. The system lacked any sort of defined file format for general purpose files, but it did define a file format for bootable cassettes. This consisted of a single extra packet at the start of the file, using only the first six bytes of the payload and filling the rest of the packet with zeros. The first of these bytes was unused filler. The second byte held the number of packets in the file, allowing up to 255 packets, or 32 kB of data. The next two bytes specified

1008-586: The XL12 and XC13, sold in Poland, the Czech Republic and Slovakia . All of the versions were mechanically similar. They all used a flip-up door on the top for inserting a tape. A piece of bright orange or silver tape behind the tape window was used make the current position of the tape more visible. The 410 had a power plug and internal power supply, the 1010 used an external power supply and ring-jack plug on

1050-585: The back of the case, and the XC12 and later models were powered through the SIO cable. The 1010 added a red LED to the front to indicate power-on, while the XC12 lacked the power LED but added one on top that lit while writing. Several other companies produced compatible drives for the Atari machines, notably General Electric 's Compu-Mate Computer Data Recorder, the Taihaho Computer Cassette and

1092-464: The cassette was the only cost-effective storage medium, the performance of the system was a serious problem. This led to a wide variety of software and hardware upgrades to improve performance. Among the best known was the Turbo 2000 system from Czechoslovakia , which increased the basic data rate of an XC12 to 2270 bit/s, almost four times as fast as the original standard. In 1983, Carl Evens posted

1134-440: The chain to counteract attenuation (the natural loss of energy in such a system). Digital signals between devices may also travel on a simple electrical bus, in which case a bus terminator may be needed on the last device in the chain. However, unlike analog signals, because digital signals are discrete , they may also be electrically regenerated, but not modified, by any device in the chain . Some hardware can be attached to

1176-402: The channel and then played back through the television speaker. This was originally used with a series of computer aided instruction (CAI) cassettes that were sold by Atari and later by third parties. It was also sometimes used on bootable cassettes to provide music while the program loaded. When used for CAI, a simple protocol was used to control playback. Each section of audio was marked with

1218-476: The communications bus at a time. Any particular daisy chain forms one of two network topologies: Users can daisy chain computing sessions together. Using services such as Telnet or SSH , the user creates a session on a second computer via Telnet, and from the second session, Telnets to a third and so on. Another typical example is the "terminal session inside a terminal session" using Remote Desktop Protocol . Reasons to create daisy chains include connecting to

1260-428: The drive. These included pin 8, MOTOR, that turned the tape drive motor on and off, and pin 11, AUDIOIN, which passed through any audio recorded on the left audio channel into the system. Data was read and written to the right audio channel using the standard SIO data pins, pin 3, DATAIN and pin 5, DATAOUT. Because there was no way to decode commands or perform device selection, any single host computer could only support

1302-401: The effective rate somewhat, to perhaps 550 bit/s. This compares favorably to similar systems of the era, like the 300 bit/s Kansas City Standard or the formats used on the TI-99/4 or Commodore Datasette , which had similar signaling rates as Atari but wrote all data twice as an error correction mechanism and thus had effective rates closer to 300 bit/s. In those markets where

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1344-482: The elementary stream between PES packet headers. A typical method of transmitting elementary stream data from a video or audio encoder is to first create PES packets from the elementary stream data and then to encapsulate these PES packets inside an MPEG transport stream (TS) packets or an MPEG program stream (PS). The TS packets can then be transmitted using broadcasting techniques, such as those used in an ATSC and DVB . In order to provide mono compatibility ,

1386-596: The entire content inside the envelope, and the footer would be your signature at the bottom. Network design can achieve two major results by using packets: error detection and multiple host addressing . Communications protocols use various conventions for distinguishing the elements of a packet and for formatting the user data. For example, in Point-to-Point Protocol , the packet is formatted in 8-bit bytes, and special characters are used to delimit elements. Other protocols, like Ethernet, establish

1428-533: The keyboard to indicate the drive was ready. The system would then assert the MOTOR line to begin playback, reading from the tape for up to 35 seconds looking for the header packet. If it was not found, or some other type of packet was found, an error was reported. Another feature of the Atari SIO port was the AUDIOIN pin, which was connected to the left channel of the cassette. This allowed audio to be recorded to

1470-456: The later-model 410's in the new silver-grey XE coloring. Only small numbers seem to have been produced, as by this time floppy disks were now almost universal in the US and most of Europe. The XE line was later sold primarily in eastern Europe, South America and other markets that had not previously seen low-cost home computers . These markets remained highly cost sensitive and the cassette recorder

1512-508: The protocol used for the transmission of spacecraft instrument data over the deep-space channel. Under this standard, an image or other data sent from a spacecraft instrument is transmitted using one or more packets. Packetized elementary stream (PES) is a specification associated with the MPEG-2 standard that allows an elementary stream to be divided into packets. The elementary stream is packetized by encapsulating sequential data bytes from

1554-437: The start of the header and data elements by their location relative to the start of the packet. Some protocols format the information at a bit level instead of a byte level. A packet may contain any of the following components: IP packets are composed of a header and payload. The header consists of fixed and optional fields. The payload appears immediately after the header. An IP packet has no trailer. However, an IP packet

1596-458: The starting location of where to place the data in memory, and the final two held the location to jump to, to start the program running. When the system was booted with the Start key held down, the computer would attempt a cassette boot. This would play a tone on the television speaker to indicate the computer was ready, at which point the user would press Play on the drive and then press any key on

1638-405: The two outputs would toggle DATAIN on and off, which was automatically interpreted by the POKEY and reformed into a series of bytes for storage. While most systems of the era wrote bytes of data with no particular overall format, Atari's driver used a simple packetized format to aid in error detection . Data was split into packets of 128 bytes and then sent to the tape with three header bytes and

1680-420: The wiring patterns embedded inside of devices. Other examples of devices which can be used to form daisy chains are those based on Universal Serial Bus (USB), FireWire , Thunderbolt and Ethernet cables. For analog signals , connections usually consist of a simple electrical bus and, especially in the case of a chain of many devices , may require the use of one or more repeaters or amplifiers within

1722-676: Was intended to allow the computer to perform more complex processing of the data, allowing it to stop the transfer and thereby giving it any amount of time needed. Normal IRG was not widely used, the only known examples being assembly language programs be loaded in ATASCII format, and the much more rarely used ability to load and store BASIC programming language as text. When stored as text, each line had to be read in and then converted to tokenized format, which could take some time. Generally, BASIC programs were instead stored in their tokenized form which could be read and written as binary data using

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1764-477: Was still a viable system. Most sets from this era are variations on the XC12, using a Phonemark PM-4401A mechanism, the same unit as the Commodore Datasette . This was sized between the 410 and 1010 and was sold in all of Atari's markets. Several versions of the XC12 were also produced for specific markets, differing primarily in labelling. In Poland, they could be found as the XCA12 or CA12. A later modification led to

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