Test mode 3 - display UART mode and host to TTY/VGA loopback

A project log for Custom circuit testing using Intel HEX files

Download / upload memory contents into computer motherboards or other devices for test or debugging (using 3 micro-coded controllers)

zpekiczpekic 12/08/2021 at 05:170 Comments

To have confidence in a test circuit, it is useful for the test circuit to test itself :-) This mode:

UART is two separate circuits (SER2PAR and PAR2SER) that I reuse in many projects. They support a variety of 8-bit per character transmit and receive frames. The terminal program on the host should be set to same setting (8-N-1 in this case)

Anvyl board switches 2..0 select the mode as visible in the image below.

(note 700ms delay per line - this is to allow time for the trace of HEX2MEM microcode to display before processing next incoming character, more about this below)

To simplify top level object, the TTY, video RAM, chargen RAM and VGA controller are wrapped up in one component called TTY2VGA: