Xerox WorkCentre XK50cx, Service Manual

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4-3
Circuit
EXTERNAL DMA
It brings data from an external device (DUOIP:U16) using DMA channel 0. DMA REQUEST (U15 - 137 or U16 -
4) sent from an DUOIP2(U16) to KS32C6400 activates DMA ACKNOWLEDGE (U15 - 138 or
U16 - 3) signal and drives DMA channel 0 to produce CHIP SELECT and READ STROBE (/RD) at the external
device and bring data from it. It generates address of destination memory, CHIP SELECT and WRITE
STROBE (/WR) in order to move this data into destination memory, and then stores the data.
Fig.4-1-2 EXTERNAL DMA TIMING DIAGRAM