Search found 69 matches

by S_U_C
Sun Apr 03, 2022 3:16 pm
Forum: Hardware
Topic: FAULTY VIDEO DISPLAYS
Replies: 0
Views: 4297

FAULTY VIDEO DISPLAYS

I worked out a mechanism for the repeating screen patterns on the MZ80K and MZ80A. The Z80 is in a endless loop reading RST instructions. The MZ80A REPEATING VERTICAL LINE PROBLEM i,e.char 39 + blank RST CODE ADDRESS PUSHED ON TO STACK 0000h c7 1100 0111> 0000 0001 + 0000 0000 char 1 + blank 0008h c...
by S_U_C
Fri Mar 04, 2022 4:23 pm
Forum: Assembly
Topic: HBLANK (MZ-80A)
Replies: 25
Views: 12588

Re: HBLANK (MZ-80A)

I am a K pearson not a A There is no snow on the K unless people directly poke/write data to the screen. Printing to the screen uses the V-HBlank signal. to sycronhise the writting. And I expect the other machines do the same. The K as no wait signal. If code is copied from the ROM into RAM on the K...
by S_U_C
Fri Mar 04, 2022 1:14 am
Forum: Assembly
Topic: HBLANK (MZ-80A)
Replies: 25
Views: 12588

Re: HBLANK (MZ-80A)

PS
There is no wait states for RAM, VRAM or ROM on the MZ80A
It is used by the EXWAIT via the bus e.g the FD card add a 1 clock pulse for FDROM access
by S_U_C
Fri Mar 04, 2022 1:01 am
Forum: Assembly
Topic: HBLANK (MZ-80A)
Replies: 25
Views: 12588

Re: HBLANK (MZ-80A)

I have just had a look at the MZ80A monitor and the tempo $E008 is tested with a RRCA so it is D0, you are correct. The miss- print is on page 163 were it states tempo D7 HBlank D0 I would still test using a mask + AND LD A,80H HBLK1:AND (HL) ; if (HL) = 1 ? ? ? ? ? ? ? A = 80H / if (HL) = 0 ? ? ? ?...
by S_U_C
Thu Mar 03, 2022 5:18 pm
Forum: Assembly
Topic: HBLANK (MZ-80A)
Replies: 25
Views: 12588

Re: HBLANK (MZ-80A)

I see your point.
I think the diagram 3.10 is incorrect.
Plus you can only detect 1 pluse after the Vblank
and the tempo is slow pulsing
by S_U_C
Thu Mar 03, 2022 5:04 pm
Forum: Assembly
Topic: HBLANK (MZ-80A)
Replies: 25
Views: 12588

Re: HBLANK (MZ-80A)

I am not saying you can not detect a pulse with your code but it is the tempo signal from a 556 timmer for the sound not the video Hblank See page 163 of the Owners Manual . The Hblank signal from the video goes through a re-triggerable mono-stable to generate a fixed length pulse using capacitors a...
by S_U_C
Thu Mar 03, 2022 11:45 am
Forum: Assembly
Topic: HBLANK (MZ-80A)
Replies: 25
Views: 12588

Re: HBLANK (MZ-80A)

LD A,$7F HBLK1: CP (HL) JP C,HBLK1 is 24 T-cycles loop is 17 LD A,1 HBLK1:AND (HL) ; if (HL) = ? ? ? ? ? ? ? 1 A = 1 / if (HL) = ? ? ? ? ? ? ? 0 A = 0 JP NZ, HBLK1 is 24 T-cycles loop is 17 HBLK1:LD A,(HL) RRCA JP C,HBLK1 is 21 T-cycles loop is 21 My code will find Hblank on D0 Your code will not fi...
by S_U_C
Mon Feb 28, 2022 5:42 pm
Forum: Assembly
Topic: HBLANK (MZ-80A)
Replies: 25
Views: 12588

Re: HBLANK (MZ-80A)

0E008H D0 is the hblank signal
so why not isolate bit with
LD A,1
AND (HL)
and test the Z flag

or you could
LD A,(HL)
RRCA
and test the C flag
by S_U_C
Tue Feb 22, 2022 6:59 am
Forum: Hardware
Topic: Correct tape type
Replies: 12
Views: 6301

Re: Correct tape type

I used C 60 cassettes and higher in the past with no problem. But extra drag can build up with use, with repeat forward wind to counter xxxx and load program, there may have been rewinds to lower tape counter setting to. You could try fast wardwarding and fast rewinding the whole tape a few times to...
by S_U_C
Mon Feb 21, 2022 5:00 pm
Forum: Hardware
Topic: Correct tape type
Replies: 12
Views: 6301

Re: Correct tape type

Have you tried the suspect tapes in another machine ?