Z80189 Datasheet, PDF (26/107 Pages) Zilog, Inc. – GENERAL-PURPOSE EMBEDDED CONTROLLERS

Zilog
PC DMA TIMING DIAGRAMS
PC Clock
Internal
HDRQR
HDRQ
PRELIMINARY
Z80189/Z8L189
GENERAL-PURPOSE EMBEDDED CONTROLLERS
(1)
/AEN
/HDACK
/HWR
2
1
HD [0:7]
Valid
(1) The HDRQ will not fall inactive until it ses the
falling edge of /HWR during the /HDACK cycle.
3
4
5
Figure 28. PC DMA Write: Memory-Read, I/O Write
DMA Bus Cycle on PC AT Bus
PC Clock
Internal
HDRQR
(1)
HDRQ
/AEN
/HDACK
2
1
/HRD
HD [0:7]
Valid
(1) The HDRQ will not fall inactive until it sees the
falling edge of /HRD during the /HDACK cycle.
3
4
6
5
Figure 29. PC DMA Read: I/O-Read, Memory-Write
DMA Bus Cycle on PC AT Bus
26
DS971890301