6. DMA Controller
ÛZIATECH
45
DMA CHANNELS
The DMA channels are summarized below.
Backplane:
DMA service is available for the BUSRQ*/BUSAK signals on the
STD backplane. This channel is required by the STD bus floppy disk
controller and uses DMA channel 2. If a floppy disk controller is not
used in the system, DMA channel 2 may be used for other
peripherals. Note that if the optional local floppy option is selected it
will use DMA channel 2, making the backplane DMA channel
unavailable to the ZT 8907.
Frontplane:
Three channels of DMA are accessible through frontplane connector
J6. The three frontplane channels are independently selectable
(through cuttable traces CT16, CT17, CT25, CT29, and CT39) for 8-
bit or 16-bit operation. One frontplane channel supports DMA
channels 0 or 5. The second frontplane channel supports DMA
channels
1 or
6. The third frontplane channel supports DMA
channels 3 or 7. Be sure to mask the channels not required by the
application.
Local:
The onboard IEEE 1284 Parallel Port (see Chapter 9 "
") can be configured to use DMA channel 3 for data
transfers.
