ST10F269ZX Datasheet, PDF (65/184 Pages) STMicroelectronics – 16-BIT MCU WITH MAC UNIT, 128K to 256K BYTE FLASH MEMORY AND 12K BYTE RAM

ST10F269
12 - PARALLEL PORTS
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 Buffer 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 intra-segment
address or the 8/16-bit data information. The
incoming data on PORT0 is read on the line
Figure 22 : Block Diagram of a PORT0 Pin
“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.
The Figure 22 shows the structure of a PORT0
pin.
Write DP0H.y / DP0L.y
Direction
Latch
Read DP0H.y / DP0L.y
Write P0H.y / P0L.y
Port Output
Latch
Alternate
Direction
1
MUX
0
Alternate
Function
Enable
Alternate
Data
Output
Port Data
Output
1
MUX
0
Output
Buffer
P0H.y
P0L.y
Read P0H.y / P0L.y
1
MUX
0
Clock
Input
Latch
y = 7...0
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