Looking for the core Z180 SC131 Serial Port initilization code.

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John Monahan

May 11, 2023, 5:16:39 PM5/11/23
to retro-comp
I have version of the SC131 board working on an S100 bus board (see below) with the  well known SC131-RomWBW-SC180-131-v320-2023-21.rom code in the Flash RAM.
The serial port works fine at 115,200 baud on this board. It boots up CPM etc.

I am trying to write a small RAM based Z180 monitor to interface with other S100 boards using the above circuit.  The problem I'm having is cannot get the Z180 serial port to work with any Z180 serial port A initialization code I write.

I have been unsuccessful in looking over the thousands of lines of code on web sites for the above SC131 ROM to find the actual core lines to initialize the Z180 serial port to 115K baud.  It should be no more than 8 lines of assembly code.  Could somebody locate it for me (and if present) where the relevant equates actually are.    Also if present the relevant console I/O routine. 
Thanks in advance

V0.2 Z180 Prototype (Small).jpg

Ed Brindley

May 12, 2023, 3:26:19 PM5/12/23
to retro-comp
The RomWBW Z180 driver asci.asm is here: https://github.com/wwarthen/RomWBW/blob/dev/Source/HBIOS/asci.asm
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