Once I have encountered such a problem: all the bytes I write into the FIFO are zeros.
I found external microprocessors can't drive 68013A's databus easily. even the external microprocessors drive all the databits high. the voltage on the databus is only 0.7 volt.
it's so strange.
so i was angry, i added the 16244a to drive the datat bus, that time the 16244a finally drive the data bus to high as i want.
however, the 68013 is very hot.
it became stranger.
I read the datasheet of 68013 again. i found out the 68013's digital gate is CMOS gate, it can be drive high easily theoretically.
I don't know why it is so.
finally one time i found out the SLOE is unconnect, immediately i understand that i set the SLOE is active high ,but the unconnect pin is always about 2.4volt.
so i pull down the SLOE pin . and the problem is resolved.
Thanks for sharing your debugging experience here. Appreciate it.