The code repo contains test programs and utilities to turn up the board and start development.

test2a-rom-led.asm

The ROM LED test program is burned into the EEPROM at starting address 0000H. This program blinks an LED connected to SOD and verifies the basic wiring of the 8085, the address latch, and the EEPROM data and lower address lines.

Note that this program starts with a JMP instruction to clear the reset flip-flop. This isn’t needed, but means that the program will also work if the final address decoding hardware is installed.

test2b-rom-address.asm

The ROM address test program can be run to verify that all of the upper ROM address lines have been connected correctly. It will flash the LED at different speeds for a successful test or do a continuous fast blink on failure.

test3-rom-serial.asm

With an FTDI interface connected to the SOD, the ROM serial test program writes a continuous stream of the ‘T’ character to the serial port by bit-banging async data to the port.

Note that this program uses timing loops that are dependent on the frequency of the clock crystal. A different crystal would require different delay loop values. The connected termnal should be set for 9600bps.

test4-ram-serial.asm

The RAM serial test program writes a continuous string of A to Z characters to the serial port. This uses RAM to store the character to be sent, so it verifies that the RAM is wire correctly.

loader.asm

Code development can be sped up with the use of the Hex Loader. This can be burned into the ROM and will load and execute programs from RAM. While not as powerful as a full monitor, it does remove the need to power down the system and remove the ROM for each code update. It accepts Intel Hex files from asm85 or other tools that write in the standard format.

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