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PCMCIA Interface
17-8
MPC823 USER’S MANUAL
MOTOROLA
PCMCIA
INTERFACE
17
17.4.3 Interrupts
Each input from the PCMCIA card to the host (BVD,CD,RDY, and VS) is sampled in the
PCMCIA interface input pins register (PIPR) and any change to these bits is reported in the
PCMCIA interface status change register (PSCR). The contents of the PSCR is AND’ed with
the PCMCIA interface enable register (PER) to generate a PCMCIA interface interrupt. You
can program the interrupt level for the exception that is generated. The PCMCIA interface
can generate an additional interrupt for the RDY/IRQ signal. This interrupt can be generated
for level (low or high) and for change (fall or rise) of the input signal.
17.4.4 Power Control
You can perform a write cycle using one of memory controller’s CS signals, so that you can
operate an external device to provide a regulated source voltage to the PCMCIA slot. There
are a number of such devices available. However, auto-power control is not supported.
17.4.5 Reset and Three-State Control
You can write to the right bit in the PCMCIA general interface control register B (PGCRB)
and cause the PCMCIA card to be reset or to disable the output drive of the external latches.
17.4.6 DMA
The MPC823’s DMA module with the CPM microcode provides two independent DMA
channels. The PCMCIA module can be programmed to generate control for an I/O device
implemented as a PCMCIA card to act upon a DMA transfer. You can use the PRS field in
the appropriate POR to program any window to be a DMA window. The PCMCIA controller
supplies the signaling for the socket. DMA to or from the PCMCIA interface is done through
dual-access DMA transfers. DMA requests can be supplied through the SPKR, IOIS16_B or
INPACK signals. To support the DMA function, the slot’s INPACK should be connected to
DREQ2. The actual source used for a DMA request is programmed in the CBDREQ[0:1]
field of the PGCRB register. If the internal DMA request is enabled, then port C should be
programmed to not DREQ2. When the internal DMA request is disabled, then the DMA
request is assumed to be DREQ2. In this case, you should program port C so that the PC14
pin is DREQ2.
Note: The PCMCIA controller will monitor the SDACK2 signal internally to meet the
IDMA handshaking protocol. Therefore, you do not have to monitor this signal for
your PCMCIA design.