The MC6840 is a Programmable Timer Module. It has three 16-bit binary counters. The timers can be independently clocked, either from the E clock or from an external source.
In addition to the MC6840 IC, there is a 74574 latch. The latch is used by the cpu to control the three hardware gates on the PTM. Bits 0,1,2 of the data bus control gates 1,2,3.
A F16V8 PAL does the address decoding and card selection.
I provided header pins for the three timer outputs, the three timer input clocks, and some ground pins.
The H1 jumper selects between two possible PTM cards.
The J2 jumper selects which interrupt will occur, IRQ or NMI.
This board is version 1.0, making it the first board to work on the first attempt!
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