ZLoader Configuration Switches - peterw8102/Z80-Retro GitHub Wiki

The main CPU card has three DIP switches which are read into the top 3 bits of input port 64h

ZLoader checks these three bits on start up.

Bits 0 and 1 are used to choose the boot mode. Bit 2 determines whether the default input console will use the serial port (SIO/A) or the VDU/Keyboard combination:

Bit 1-0	Boot mode
00	Boot into ZLoader command line
01	Boot default image from Raspberry Pi via the serial block protocol.
10	Boot OS image 1 from the SDCard inventory (use to boot, for example, directly into CP/M
11	Reserved - currently treated the same as 00

If bit 2 is 0 then the default console (for ZLoader) is serial port A.

If bit 2 is 1 then, assuming there is a video card and Omega keyboard attached, this will be used as a console device.