Chapter 4
I/O Ports
IV - 52
Synchronous Output (Port 4)
4-12-3
Operation
nSynchronous Output Setup
The synchronous output control register (P4SYO) selects the synchronous output pin of the port 4, in
each bit.
The synchronous output event is selected by the pin control register (FLOAT).
When the external interrupt 2 (IRQ2) is selected, the interrupt edge should be specified. The interrupt
edge can be specified by the external interrupt 2 control register (IRQ2ICR) or the both edges interrupt
control register (EDGDT). The synchronous output recognizes the generation of the specified edge as
an event.
nSynchronous Output Operation
When the synchronous output control register (P4SYO) is set to disable the synchronous output (I/O
port), the port 4 is functioned as a general port. When the port 4 is set to disable the synchronous output,
the same value to the port 4 output register (P4OUT) is always loaded to the synchronous output value
stored register. [
Figure 4-12-1. Synchronous Output Control Block Diagram ]
After the output mode is selected by the port 4 direction control register (P4DIR), if the synchronous
output is enabled by the synchronous output control register (P4SYO), the value of the synchronous
output value stored register is output from pins. If the synchronous output event that is set by the pin
control register (FLOAT) is never generated, the synchronous output value stored register holds the
same value when the synchronous output event is enabled.
Store the value that should be output from pin after the synchronous output event is generated, to the
port 4 output register (P4OUT). Once the synchronous output event that is set by the pin control register
(FLOAT) is generated, the data of the synchronous output value stored register is switched to the data of
the port 4 output register (P4OUT), and the output value from pin is changed.
Table 4-12-2
Synchronous Output Event
Before the synchronous output is enabled by the synchronous output control register
(P4SYO), set the initial value of the synchronous output to the port 4 output register
(P4OUT), in advance.
Specify to
Page
Synchronous output port
Port 4
IV - 27
Output event
External interrupt 2
(IRQ2)
III - 19, 38
Timer1
VI -32
Timer2
VI -32
Timer7
VII - 55