Briel Computers Altair 8800 micro - Appendix B: the Expansion Port

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ALTAIR 8800 micro Users Manual

Appendix B: The expansion port

Signals Description Direction

A0-A15 address bus signals Output

D0-D7 Data bus signals Bidirectional

R/W Read or Write mode Output

I/O I/O or RAM mode (high=I/O) Output

ALE Address Latch Enable Output

CS RAM chip select (low select) Output

R1 System RESET Input

SB1-3 Switch bank select Output

LLE Status LED Latch Enable (low) Output

TXD TTL Level RS232 transmit port Output

RXD TTL Level RS232 receive port Input

The expansion port is a 40 pin header located near the front of the mainboard. It uses standard bus signals to

create add-on boards. The original design did not include the expansion port and there are currently no add-on

boards available. There will be plans in the future for an addition 32K RAM board and a serial port with

onboard terminal eliminator.