Z80 Build From Scratch

Test the BB Computer:

The screenshot on the right shows the UART setup up to echo the user's keystrokes. The user has used Tera Term Send File function under the File column to send the license.txt file at 9600bps. This required a minor change to the code such that the Divisor in line 49 was changed from $60 to $0C to increase the speed from 1200bps to 9600bps.

UART_Echo-test_9600.asm

Eagle Schematic v1.0

Eagle Board Layout v1.0

Eagle PCB v1.0

(Click to enlarge)

You may notice that we have added a 1.8432MHz crystal oscillator (QG1) "can" to top right side of the board and a jumper (JP13) to the top left side of the board. The jumper will allow us to switch between slow (<100Hz) and fast (1MHz) clocks. Both will require resetting the system to ensure it will work properly.