[Techtoolslist] 9010A Z80 pod and the !IORQ line

[John Robertson]

On Feb 11, 2024, at 2:31 PM, davids at oz.net wrote:
> 
> Z80 pod and the !IORQ line. Working on a GamePlan MPU-2 board. 
> 
> 
> 
> Address space looks like:
> 
> 0x0000-0x1000 ROM
> 
> 0x0004 8255 Port A
> 
> 0x0005 8255 Port B
> 
> 0x0006 8255 Port C
> 
> 0x0007 8255 Control
> 
> 0x0008 Z80 CTC Ch1
> 
> 0x0009 Z80 CTC Ch2
> 
> 0x000A Z80 CTC Ch3
> 
> 0x000B Z80 CTC Ch4
> 
> 
> 
> Looking over the schematic I can see that the chip select lines for the 8255
> and CTC are tied the Z80 !IORQ pin (20).
> 
> 
> 
> Makes sense, only interface with the two peripherals when you need too so
> you can overlap the address space. 
> 
> 
> 
> But from the 9010A how do I control that I am reading / writing to those
> devices?
> 
> 
> 
> Thanks,
> 
> David
> 
> 

Z80 IO requests are above FFFFh. I think they are 10000 to 10003h as I recall.

The Z80 pod manual covers this…

John :-#)#

> 
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