C165UTAH Datasheet, PDF (149/539 Pages) Infineon Technologies AG – EMBEDDED C166 WITH USART IOM-2 AND HDLC SUPPORT

C165UTAH
Parallel Ports
8.2.1 Alternate Functions of PORT1
When a demultiplexed external bus is enabled, PORT1 is used as address bus.
Note that demultiplexed bus modes use PORT1 as a 16-bit port. Otherwise all 16 port
lines can be used for general purpose I/O.
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.
Alternate Function
P1H
PORT1
P1L
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
a)
A15
A14
A13
A12
A11
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
General Purpose
Input/Output
8/16-bit
Demux Bus
Figure 31 PORT1 I/O and Alternate Functions
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 becomes active.
Figure 32 shows the structure of a PORT1 pin.
Data Sheet
149
2001-02-23