scommstech
Experienced Member
- Joined
- Jul 16, 2007
- Messages
- 69
Hi
Need to pick somebodys brains on what conditions an 8088D needs for
it to start up.
I have a faulty XT clone motherboard. Its a standard non turbo board.
clock Xtl 14.38Mh The All chips are soldered in apart from
the 8088D (no 8087). the board is dead. All voltages are ok and the clock is
running. I have a logic analyzer on the 8088. The results after
triggering the analyzer on the reset are.
(Reset) pin 21 goes high and then low (stays low).
(Clock) pin 19 looks ok Good mark space ratio
(Ready) pin 22 is high (stays high)
(Int) pin 18 is low (stays low)
(NMI) pin 17 is high (stays high, does not go low to high)
S0,S1,S2 pins 26,27,28 are all high and show no activity.
I don't think any other pins can stop an 8088 resetting.
The 8088, after doing its own internal reset should vector to
FFFF0 and read in an instruction.
To do this it must issue a read cycle and the S0,S1,S2 must show some
activity.
I'm using a RACER II diagnostic card to test the boards.
A good board I tested had all the same pin conditions but shows activity
on the S0,S1 pins. S2 stays high (I think the diag card then takes over)
I have changed the 8088 but it's the same.
What am I missing.
I'd appreciate it if somebody can throw some light on this as I'm out of ideas.
regards
Scommstech
Need to pick somebodys brains on what conditions an 8088D needs for
it to start up.
I have a faulty XT clone motherboard. Its a standard non turbo board.
clock Xtl 14.38Mh The All chips are soldered in apart from
the 8088D (no 8087). the board is dead. All voltages are ok and the clock is
running. I have a logic analyzer on the 8088. The results after
triggering the analyzer on the reset are.
(Reset) pin 21 goes high and then low (stays low).
(Clock) pin 19 looks ok Good mark space ratio
(Ready) pin 22 is high (stays high)
(Int) pin 18 is low (stays low)
(NMI) pin 17 is high (stays high, does not go low to high)
S0,S1,S2 pins 26,27,28 are all high and show no activity.
I don't think any other pins can stop an 8088 resetting.
The 8088, after doing its own internal reset should vector to
FFFF0 and read in an instruction.
To do this it must issue a read cycle and the S0,S1,S2 must show some
activity.
I'm using a RACER II diagnostic card to test the boards.
A good board I tested had all the same pin conditions but shows activity
on the S0,S1 pins. S2 stays high (I think the diag card then takes over)
I have changed the 8088 but it's the same.
What am I missing.
I'd appreciate it if somebody can throw some light on this as I'm out of ideas.
regards
Scommstech