ST10R272L - PARALLEL PORTS
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outputting the address. During external accesses in demultiplexed bus modes PORT0 reads
the incoming instruction or data word or outputs the data byte or word.
When an external bus mode is enabled, the direction of the port pin and the loading of data
into the port output latch are controlled by the bus controller hardware. The input of the port
output latch is disconnected from the internal bus and is switched to the line labeled
“Alternate Data Output” via a multiplexer. The alternate data can be the 16-bit intrasegment
address or the 8/16-bit data information. The incoming data on PORT0 is read on the line
“Alternate Data Input”. While an external bus mode is enabled, the user software should not
write to the port output latch, otherwise unpredictable results may occur. When the external
bus modes are disabled, the contents of the direction register last written by the user
becomes active.
Figure 27 PORT0 I/O and alternate functions
P0H.7
P0H.6
P0H.5
P0H.4
P0H.3
P0H.2
P0H.1
P0H.0
P0L.7
P0L.6
P0L.5
P0L.4
P0L.3
P0L.2
P0L.1
P0L.0
PORT0
D7
D6
D5
D4
D3
D2
D1
D0
P0H
P0L
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
AD15
AD14
AD13
AD12
AD11
AD10
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
AD1
AD0
AD15
AD14
AD13
AD12
AD11
AD10
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
AD1
AD0
Alternate Function
a)
b)
c)
d)
General Purpose
Input/Output
8-bit
Demux Bus
16-bit
Demux Bus
8-bit
MUX Bus
16-bit
MUX Bus