Memory Maps
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2-7
2
DMA Channels
The PBC supports seven DMA channels. Channels 0 through 3 support 8-
bit DMA devices. Channels 5 through 7 are dedicated to 16-bit DMA
devices. The channels are allocated as follows:
Sources of Reset
The MCP750 SBC has five potential sources of reset:
1. Power-on/Undervoltage Reset.
2.
Front Panel RESET
switch (will generate a hard reset when
depressed).
3. Watchdog timer Reset function controlled by the SGS-Thomson
MK48T559 Watchdog Timer or the Raven Watchdog Timer.
4. Port 92 Register via the PBC
5. CompactPCI Bus via the 21154 Bridge Control Register.
Table 2-2. PBC DMA Channel Assignments
PBC
Priority
PBC
Label
Controller
DMA Assignment
1
Channel 0
DMA1
Serial Port 3 Receiver (Z85230 Port A Rx)
2
Channel 1
Serial Port 3 Transmitter (Z85230 Port A Tx)
3
Channel 2
Floppy Drive Controller
4
Channel 3
Parallel Port
5
Channel 4
DMA2
Not available — Cascaded from DMA1
6
Channel 5
Serial Port 4 Receiver (Z85230 Port B Rx)
7
Channel 6
Serial Port 4 Transmitter (Z85230 Port B Tx)
8
Channel 7
Not Used
