CPU pin 39, UA10 pin 8, UA5 pin 1
All attached - all the same
UF6 pin 7, UE7, UE8 pin 19s
No activity even straight after pwoer on any any of these three pins. The go straight high.
Colin.
Quote:
Originally Posted by SiriusHardware
The Φ1 signal from the CPU is officially 'NC' on the PET so we don't have to follow that.
Φ2 on the other hand does get about a bit. After passing through buffer A10 pins 9/8 it becomes signal 'BØ2' which we can assume stands for 'Buffered Φ2'.
'BØ2' goes to UC6 (6520) on sheet 2 (IEE 488 interface), It goes to UC5 (6522) and UC7 (6250) in the keyboard scanning circuit, and it does go to the video logic area (sheet 7) where it arrives, or should, as BØ2 on UA5 pin 1.
So it may be worth looking for the Φ2 signal on
-The CPU pin 39, which I am sure we have checked before
-UA10 pin 8
-UA5 pin 1
Also look for activity specifically on the 'TV RAM R/W' line during the post-reset phase to see if the CPU is attempting to clear the video RAM.
-UF6 pin 7
-UE7, UE8 pin 19s
Does anyone recall if the cursor on the PET's initial screen blinks or is steady-state?
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