[Techtoolslist] Fluke 9010 and Gorf / Wizard of War etc.

[John Robertson]

On 2022/03/26 10:07 p.m., davids at oz.net wrote:
> Working on a stack of these boards.  There is no watch dog disable but it is
> an easy enough thing to do by removing Q10 (the WD then can't toggle reset).
>
>   
>
> With the Fluke connected
>
> I can run UUT and game will run fine
>
> I can test the Video Dram from 0x4000-0x7FFF no problem.
>
> I can test the cpu SRam from 0xD080-0xDFFF no problem.
>
>   
>
> The cpu SRam from 0xD000-0xD07F though give a data error when trying to
> write to it.
>
>   
>
> >From the mame memory map it shows that ram 0xD000-0xD03F is protected_ram (I
> think this is a typo because it is blocked for me to 7F).
>
>   
>
> Looking though the tech tools list history I saw mention from Kev in 2004
> that there is a section of the ram that has a latch attached to reset.  I
> think that is the protected ram mentioned in the memory map.
>
>   
>
> The map also says address 0xA55B controls the protection.
>
>   
>
> Looking at the gorf schematic page 63 (the rom/ram board) I can see the
> latch Kev mentioned.
>
>   
>
> U9:11 (74LS74) controls the chip select for X21 / X22.  And this is tied to
> reset so would clear if the WD were to kick (but I have disabled it)
>
>   
>
> This is in turn fed by U10:9 (74LS133) which takes in a bunch of address /
> control lines and's them and inverts.  So if anything isn't set it will
> output false.
>
>   
>
> One of those intputs (pin 4) is from U16:13 a MC14078 (8 input NOR).
> Ensuring that a bunch of other things are not set which gives us a enable
> latch of A55B.
>
>   
>
> Problem I am having is one of the inputs to U16 is pin 5 which it IORQ!.
>
>   
>
> When I try to write to A55B with fluke to latch that the memory protect,
> IORQ! Is always high.  So U16:13 is low, which make U10 fail the and.
>
>   
>
> I verified IORQ! Is working (I can run the UUT) and see it toggle.
>
>   
>
> Reading the spec's on the Z80 control signals I think that should be pulled
> low whenever the CPU is doing a write.  But it's not when doing so from the
> fluke.
>
>   
>
> I could jumper U10:4 to ground in some manner but would rather understand
> what is happening.
>
>   
>
> Ideas?
>
>   
>
> Thanks,
>
> David

Isn't IORQ! only active when you are above FFFFh? Very rusty on Z80 
coding, and looking through the Osborne's Some Real Micros isn't helping 
my memory.

Check section 7 starting around page 7-16

John :-#)#

-- 
                  John's Jukes Ltd.
7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3
Call (604)872-5757 (Pinballs, Jukes, Video Games)
                  flippers.com
  "Old pinballers never die, they just flip out"