Parallel Bus Interface

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Parallel Bus Interface (above) and Enhanced Cartridge Interface (below, with cartridge socket). Atari XL PBI and XE ECI.png
Parallel Bus Interface (above) and Enhanced Cartridge Interface (below, with cartridge socket).
European 800XL with Parallel Bus Interface visible (above, with cover removed) and 130XE with Enhanced Cartridge Interface (below). Atari 800XL and 130XE Rear.jpg
European 800XL with Parallel Bus Interface visible (above, with cover removed) and 130XE with Enhanced Cartridge Interface (below).

The Parallel Bus Interface, or PBI, is a 50-pin port found on some XL models of the Atari 8-bit computers. It provides unbuffered, direct connection to the system bus lines (address, data, control), running at the same speed as the 6502 CPU. The 600XL and 800XL, along with the unreleased 1400XL and 1450XLD have a PBI interface.

Contents

The Enhanced Cartridge Interface, or ECI, is a modified version of the PBI designed to be smaller and less expensive to implement. Many of the pins in the PBI are duplicated in the 30-pin cartridge slot, so ECI was limited to only those 14 pins in the PBI that were not in the cartridge slot. Placed side-by-side on the back of the computer, devices plugged into both at the same time to provide the same electrical interface as the PBI. The ECI is found on late production units of the 65XE, the 130XE, and the 800XE.

Details

The PBI is implemented as a rectangular 50-pin edge connector on the back of XL machines. The pins include all 16 address lines (A0 through A15) and 8 data lines (D0 through D7). Other pins include various electrical supplies, clock signals, interrupts, memory strobes, and even an analog audio input.

As many of these pins were already implemented as part of the already-existing 30-pin ROM cartridge slots on Atari machines, the XE series re-implemented the PBI to include only those pins that the PBI had but the cartridge slot didn't. The resulting connector contained only 14 pins, mostly the address pins A13 though A15, and the various sound and signal pins of the PBI. The ECI slot was placed beside the cartridge slot, allowing a single connector to be inserted into both connectors and re-create the functionality of the entire PBI.

Pinout

Parallel Bus Interface (PBI) - looking at the back
135791113151719212325272931333537394143454749
2468101214161820222426283032343638404244464850
Parallel Bus Interface (PBI) - Pinout
PinTOPPinBOTTOM
1GND Ground2External select
3A0 Address output4A1
5A26A3
7A48A5
9A610GND
11A712A8
13A914A10
15A1116A12
17A1318A14
19GND20A15
21D0 Data (bidirectional)22D1
23D224D3
25D426D5
27D628D7
29GND30GND
31Phase 2 clock output32GND
33NC Reserved34Reset output
35(IRQ) Interrupt request36Ready input
37NC38External decoder output
39NC40Refresh output
41Column address output42GND
43MPD Math pack disable input44Row address strobe
45GND46Latch read/write out
47NC (+5V on 600XL only)48NC (+5V on 600XL only, used for 1064)
49Audio input50GND

Devices

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References

  1. "Zrób sobie sam interfejs IDE! - Forum Atarum".
  2. "Ram 320Xl".
  3. "RAM320XE/576 order thread".