Atari 1200XL
 | |
| Atari 1200XL home computer | |
| Specifications | |
|---|---|
| Manufacturer | Atari, Inc. |
| Type | Home computer |
| Released | Announced 13 December 1982; shipped March 1983 |
| Discontinued | July 1983 (end of production) |
| Intro price | US$899 |
| CPU | Atari 6502 (modified, "SALLY", C014806) at 1.79 MHz |
| Memory | 64 KB RAM (eight 64K × 1 DRAMs) |
| Storage | Cassette and floppy drives on the SIO bus; ROM cartridges |
| Display | ANTIC and GTIA; 40 × 24 text, up to 320 × 192 pixels |
| Sound | POKEY, four channels |
| ROM | 16 KB operating system in two 8K × 8 ROMs; no built-in BASIC |
| Power | External 9 V AC transformer (31 VA); rectifier and two 78M05 regulators on the main board |
| OS / Firmware | Atari OS revision 10 or 11 (Atari's Rev. A and Rev. B) |
| Predecessor | Atari 800 |
| Successor | Atari 800XL |
| Codename | Sweet-16, "Elizabeth" |
The Atari 1200XL is a 64 KB home computer made by Atari, Inc. in 1983, the first model of the XL series. Atari introduced it at a press conference in New York on 13 December 1982, announced a price of US$899 at the Winter CES in January 1983, and shipped it in March 1983.[1] It was built in the USA from January to May 1983 and in Taiwan from April to July 1983, and only in an NTSC version for North America.[1]
At the Summer CES in June 1983 Atari introduced the Atari 600XL and Atari 800XL and announced that the 400, 800 and 1200XL would be discontinued; 1200XL production ended in July 1983.[1] From serial numbers, Karl Heller estimates that fewer than 120,000 were made, possibly fewer than 100,000.[1]
The 1200XL came out of Atari's "Sweet-16" (or "Elizabeth") project at the Atari New York lab; the case was designed by Regan Cheng.[1]
Differences from the 400/800 and later XLs
[edit | edit source]Compared with the Atari 400 and Atari 800, the 1200XL has 64 KB of RAM, a revised 16 KB operating system, a HELP key, four programmable function keys and two status LEDs.[1] It has two controller ports instead of four and no Memo Pad mode; with no cartridge and no powered drive it boots to an "ATARI" logo screen.[1] Key clicks and system beeps come from the television or monitor speaker, where the 400 and 800 have a speaker inside the case.[1]
The later 600XL and 800XL drop the function keys, the LEDs and the logo screen, but add built-in Atari BASIC and the Parallel Bus Interface, neither of which the 1200XL has.[1]
Some ports also differ. Atari's manual marks SIO pin 12 (+12 V on the 400 and 800) as not used on the 1200XL, and the monitor socket's pin 5 is not used, so there is no separate chrominance output.[2] The Atari 8-bit FAQ adds that the 1200XL is the only Atari that lacks +5 V on SIO pin 10, because of a current-limit resistor, R63.[1]
Hardware
[edit | edit source]The 1200XL has a single main board holding every chip except those on the keyboard and LED boards. The keyboard connects through a 15-conductor ribbon cable to a Molex connector, and the LED board through a 5-conductor cable.[2] The CPU is Atari's modified 6502, with a HALT input that lets ANTIC stop the processor and take the bus for display DMA.[2][1] The colour clock comes from a 3.579545 MHz crystal, Y1.[2]
RAM is eight 64K × 1 DRAMs, one per data line, of which 48 KB is directly available to programs. The operating system is in two 8K × 8 ROMs. Address decoding is done by a HAL (the "memory management unit"), a 3-to-8 decoder and a few gates.[2]
| Location | Device | Atari part number |
|---|---|---|
| U1–U6, U8, U9 | DRAM, 64K × 1 | C060612 |
| U7, U10 | 74LS158 multiplexer | C014345 |
| U11 | 74LS375 | C060613 |
| U12 | OS ROM A, 8K × 8 | C060617 |
| U13 | OS ROM B, 8K × 8 | C060616 |
| U14 | Memory management unit (HAL) | C060609 |
| U16 | 74LS14 | C016541 |
| U17 | 74LS08 | C017097 |
| U18 | 74LS138 decoder | C014344 |
| U19 | GTIA | C014805 |
| U20 | ANTIC | C012296 |
| U21 | 6502 (modified) | C014806 |
| U22 | DDU-4 delay module | C060472 |
| U23 | PIA | C014795 |
| U24 | POKEY | C012294 |
| U25 | 74LS51 | C060474 |
| U27 | CD4050B hex buffer | C010816 |
| A1, A2 | 78M05 5 V regulators | C014348 |
| A3 | RF modulator | C060618 |
| CR8 | MDA 990-2 bridge rectifier | C060534 |
The custom chips are ANTIC, the display processor, which also controls bus access and DRAM refresh; GTIA, which generates the colour and luminance signals and reads the console keys; POKEY, which handles sound, serial I/O, the paddle inputs and keyboard scanning; and the PIA, a general-purpose I/O chip for the controller ports, the LEDs and the SIO command and motor lines.[2]
Ports
[edit | edit source]The left side panel has the power switch, the cartridge slot (a 30-pin edge connector) and the two 9-pin controller jacks. The rear panel has, left to right, the SIO socket, the RF cable socket, the monitor socket, the channel 2/3 switch and the power socket.[2]
| Pin | Signal | Pin | Signal |
|---|---|---|---|
| 1 | Clock in | 8 | Motor control |
| 2 | Clock out | 9 | Proceed |
| 3 | Data into CPU | 10 | Ready (computer on) |
| 4 | Ground | 11 | Audio in (175 mV) |
| 5 | Data out | 12 | +12 V DC, not used on the 1200XL |
| 6 | Ground | 13 | Interrupt |
| 7 | Command |
The SIO bus runs at up to 19,200 baud.[2]
| Pin | Signal |
|---|---|
| 1 | Luminance |
| 2 | Ground |
| 3 | Audio output |
| 4 | Video (colour composite) |
| 5 | Not used |
The controller jacks are identical 9-pin D connectors: pins 1–4 joystick forward, back, left and right, pin 5 pot B, pin 6 trigger, pin 7 +5 V, pin 8 ground and pin 9 pot A.[2] The RF output, into 75 Ω, is 1–2 mV on channel 3 (61.25 MHz ±0.5 MHz) or channel 2 (55.25 MHz), with the sound carrier at 4.5 MHz.[2]
Keyboard and indicators
[edit | edit source]The keyboard is full-stroke, with 54 alphanumeric keys and a space bar, and eleven function keys of brushed aluminium above it: RESET, START, SELECT, OPTION, F1–F4, HELP, inverse video and BREAK. A plexiglass strip above the function keys covers three LEDs: POWER, L1 (keyboard disabled) and L2 (international character set selected).[2] F1–F4 move the cursor; with CONTROL they toggle the keyboard, the screen display, the key click and the character set.[1]
Power supply
[edit | edit source]Atari describes the 1200XL's supply as a linear supply with its electronics on the main board. An external step-down transformer supplies 9 V AC; a bridge rectifier and the regulators on the board produce separate +5 V rails for different sections of the board, with a common ground. The output of each regulator is 5 V ±5 % (1.7 A maximum), and input power is 31 VA.[2] The power adaptor is Atari part CA017964.[2] The Atari 8-bit FAQ lists the same 9 V AC, 31 VA adaptor (unit C017945, box CA017964) for the 400, 800, 810 and other devices.[1]
The 600XL, 800XL and XE machines instead take regulated +5 V DC from an external supply, so their power supplies are a different type; a 1200XL needs the 9 V AC transformer.[1] Regulator, rectifier and reservoir details are on Atari 1200XL General Maintenance.
Self test and operating system
[edit | edit source]Pressing HELP while the power-on logo is showing, with no cartridge fitted, starts the self test: Memory (ROM, RAM and ANTIC), Audio Visual (ANTIC, GTIA and POKEY), Keyboard, and All Tests.[2] In All Tests mode the keyboard test types out the programmer's name.[1] The self test was written by Mike W. Colburn.[1]
The 1200XL shipped with operating system revision 10, dated 26 October 1982, followed by revision 11, dated 23 December 1982.[1] Atari's service notes call these Rev. A and Rev. B: Rev. B corrects a fault in the System Reset key, and early production machines had the operating system in EPROMs, later ones in mask ROMs.[2]
Documentation
[edit | edit source]- Atari 1200XL Field Service Manual: Atari's field service manual FD100217, revision 01, February 1983, with theory of operation, chip pin assignments, self test and SALT 2.05 procedures, symptom checklist, disassembly, parts list and five tech tips. The scan does not include the schematics.[2]
General maintenance
[edit | edit source]Cleaning, the on-board power supply and the LED board are covered on Atari 1200XL General Maintenance.
Troubleshooting
[edit | edit source]Symptoms, the self test, SALT 2.05 and Atari's tech tips are covered on Atari 1200XL Troubleshooting Guide.
Capacitor replacement
[edit | edit source]The electrolytic capacitors, from Atari's parts list, are listed on Atari 1200XL Capacitor Replacement Guide.
Related pages
[edit | edit source]- Atari 1200XL General Maintenance
- Atari 1200XL Troubleshooting Guide
- Atari 1200XL Capacitor Replacement Guide
- Atari 1400XL
- Atari 800XL
- Atari 800
References
[edit | edit source]- ↑ 1.00 1.01 1.02 1.03 1.04 1.05 1.06 1.07 1.08 1.09 1.10 1.11 1.12 1.13 1.14 1.15 1.16 Michael Current (ed.), Atari 8-Bit Computers: Frequently Asked Questions, last modified 29 November 2009, section 1.4 "What is the Atari 1200XL?", 1.5 and 1.6 (600XL and 800XL), 1.11 (SALLY), 1.14 (designers), 1.16 (port pinouts), the power supply list, the OS ROM list and the 1982–1983 timeline. Text at faqs.org. Community reference.
- ↑ 2.00 2.01 2.02 2.03 2.04 2.05 2.06 2.07 2.08 2.09 2.10 2.11 2.12 2.13 2.14 2.15 Atari, Inc., 1200XL Home Computer Field Service Manual, FD100217, Rev. 01, February 1983. Section 1 (theory of operation, pin assignments, power supply, interfaces), section 3 (self test), section 5 (parts list), section 6 (tech tips 18 and 18A on the OS ROMs). Hosted on this wiki as Atari 1200XL Field Service Manual (PDF).