Motorola MVME5100 用户手册
IPMC7xx ISA Bus Resources
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1
ISA DMA Channels
There are seven ISA DMA channels in the PIB. Channels 0 through 3
support only 8-bit DMA devices while Channels 5 through 7 support only
16-bit DMA devices. These DMA channels are assigned as follows:
support only 8-bit DMA devices while Channels 5 through 7 support only
16-bit DMA devices. These DMA channels are assigned as follows:
Note
Because the Z85230 is an 8-bit device and Channels 5 and 6
are 16-bit DMA Channels, only every other byte (the even
bytes) from memory is valid.
are 16-bit DMA Channels, only every other byte (the even
bytes) from memory is valid.
Table 1-22. PIB DMA Channel Assignments
PIB
Priority
PIB Label
Controller
DMA Assignment
Highest
Channel 0
DMA1
Serial Port 3 Receiver (Z85230 Port A Rx)
Channel 1
Serial Port 3 Transmitter (Z85230 Port A Tx)
Channel 2
Floppy Drive Controller
Channel 3
Parallel Port
Channel 4
DMA2
Not available - Cascaded from DMA1
Channel 5
Serial Port 4 Receiver (Z85230 Port B Rx)
Channel 6
Serial Port 4 Transmitter (Z85230 Port B Tx)
Lowest
Channel 7
Not Used