ST10R272L - PARALLEL PORTS
120/320
During external accesses in demultiplexed bus modes PORT1 outputs the 16-bit
intra-segment address as an alternate output function.
During external accesses in multiplexed bus modes, when no BUSCON register selects a
demultiplexed bus mode, PORT1 is not used and is available for general purpose I/O.
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 is the 16-bit intrasegment
address. 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 become active.
Figure 29 PORT 1 I/O and alternate functions
PORT1
P1H
P1L
Alternate Function
a)
General
Purpose
8/16-bit
Demux Bus
P1H.7
P1H.6
P1H.5
P1H.4
P1H.3
P1H.2
P1H.1
P1H.0
P1L.7
P1L.6
P1L.5
P1L.4
P1L.3
P1L.2
P1L.1
P1L.0
A15
A14
A13
A12
A11
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
