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Firmware Updates
The logic on the front panel and interface boards is controlled by a state machine in a PIC16F1828 pro-
cessor. The firmware in the processor can be updated while the board set is installed in a working Altair
computer. The computer must have at least 8K of RAM and a functional 2SIO port at the standard I/O
address (10h/11h).
To update firmware, the front panel must be placed into “safe mode” by holding the AUX-Right switch in
the UP position while powering on the Altair computer. Safe mode is a fully functional version of the
firmware in a protected area of flash memory. Safe mode provides all the functions of the original Altair
front panel and also the ability to program the “normal mode” area of flash memory. Safe mode does
not rely on parameters from EEPROM and provides none of the enhanced features available in the nor-
mal mode firmware. This allows safe mode to serve as a fail-safe backup to ensure front panel function-
ality even if the normal mode code is missing, corrupted, or has a fatal bug.
To update firmware, connect a PC running a terminal emulator to the 2SIO port in the Altair. The emula-
tor should be set for 8N1 with the baud rate determined by the 2SIO board. With the front panel already
in safe mode, raise and hold AUX-Right in the up position, then raise and release AUX-Left to start the
firmware update process. A prompt from the Altair should appear on the terminal emulator window.
Follow the prompt to send the .hex file that contains the firmware update from the PC. Once the .hex
file is received, the update is automatically programmed into flash and the front panel restarts into the
updated normal mode code.
When firmware is updated, the EEPROM containing the virtual DIP switch parameters is erased to zero.
You will need to re-configure the VDIP switches to match your feature preferences.
Helpful Hints
When the firmware update mode is entered, you should notice the WAIT light turn off (or go very dim)
since the Altair is now running a small program that was injected into memory by the front panel. If the
WAIT light stays bright, this indicates the 8080 is still stopped and the injected code failed to run. This is
typically because the front panel wasn’t actually in safe mode or there is a problem with RAM in the first
8K of address space.
If the Altair is running the injected program, but you don’t have terminal response, try typing a ctrl-c on
the terminal and see if an abort message appears. If not, perform a RESET on the front panel which re-
turns the front panel to normal operation, then attempt the AUX-Right/AUX-Left entry sequence again.
Additional Notes about Safe Mode and Normal Mode
Safe mode is entered in three conditions:
1) AUX-Right is held up when the computer is powered on
2) The normal mode area of flash is erased
3) While in normal mode, RESET is raised and released while AUX-Right is held up
Note that if normal mode is functional, safe mode can be entered from normal mode by performing
item #3 above.
