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PCMCIA Interface
• Data Bus (D[0:15])—Bidirectional. Signals D0 through D15 constitute the bidirectional
data bus. The most-significant bit is D0. Significance decreases downward to D15.
• Extend Bus Cycle (WAIT_B)—Input. This signal is asserted by the PC card to delay
completion of the pending memory or I/O cycle.
• External Transceiver Direction (R/W)—Output. This signal is part of the MPC823e bus.
It is asserted or driven high during any read cycles of the MPC823e and negated or
driven low during write cycles. It is used in the PCMCIA interface to control the direction
of the data bus transceivers.
• I/O Read (IORD_B)—Output. During PCMCIA accesses, this signal is asserted in
conjunction with REG_B. It is used to read data from the PC card's I/O space. IORD_B
is valid only when the REG_B and at least one of CE1_B and CE2_B signals is
asserted.
• I/O Write (IOWR_B)—Output. During PCMCIA accesses, this signal is asserted in
conjunction with REG_B. It is used to latch data into the PC card's I/O space. IOWR_B
is valid only when the REG_B and at least one of the CE1_B and CE2_B signals is
asserted.
• Output Enable (OE_B)—Output. During PCMCIA accesses, the OE_B signal is used to
drive memory read data from a PC card into the PCMCIA socket.
• Write Enable/Program (WE_B)—Output. During PCMCIA accesses, the WE_B signal
is used to latch memory write data to a PC card in the PCMCIA socket. This signal can
also be used as the programming strobe for PC cards employing programmable
memory technologies.
• Address Latch Enable (ALE_B)—Output. This strobe signal controls the external
buffers of the Address and REG signals.
• I/O Port Is 16 Bits (IOIS16_B)—Input. When the card and its socket are programmed
for I/O interface operation, this signal is used as IOIS16_B and must be asserted by the
card when the address on the bus corresponds to an address on the PC card and the
I/O port being addressed is capable of 16-bit accesses. If the I/O region in which the
address resides is programmed as 8 bits wide, then the IOIS16_B signal is ignored.
17-4
MPC823e REFERENCE MANUAL
MOTOROLA
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