ELITE SERIES USER MANUAL

THEORY OF OPERATION

code to map out all other controllers’ ROMs without affecting itself.

This mapping of the 2K peripheral RCA space ($C800-$CFFF) is a convention maintained by nearly all of the hardware and software develop- ers.

The partitioning of the EPROM is performed by u16 (7418257) and selection of the expansion portion is done by U7 (74L574) and U16 (74LS257). Decoding of the off instruction is performed by U15 (74LS30). A synchronous approach was taken to selection design because of noise spikes on many of the bus interface lines.

7.2.5.State Machine

This consists of a program counter latch, a control latch, and a condition matrix contained in a 256/512 byte PROM. The present program counter address (which is completely independent from the 6502 central processor ‘s program count- er) and the condition lines are the inputs to the condition matrix PROM.

Separate state diagrams exist for every kind of activity allowed by the controller. These states are selected by two of the condition lines.

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