UPD784938 Datasheet, PDF (211/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 7 REAL-TIME OUTPUT FUNCTION
Figure 7-9. Interrupt Request Servicing when Real-Time Output Function is Used
Timer interrupt
Interval time setting
Set next value to be output
in P0L
Return
7.6 Cautions
(1) When P0ML and P0MH bits are set (to 1), the corresponding port output buffer is turned on and the port 0 output latch
contents are output irrespective of the contents of the port 0 mode register (PM0). The output latch contents should
therefore be initialized before making a real-time output port specification.
(2) When the port is specified as a real-time output port, values cannot be directly written to the output latch by software.
Therefore, the initial value of the output latch must be set by software before specifying use as a real-time output port.
Also, if the need arises to forcibly set the output data to a fixed value while the port is being used as a real-time output
port, you should change the port to a normal output port by manipulating the real-time output port control register (RTPC),
then write the value to be output to the output latch.
Preliminary User’s Manual U13987EJ1V0UM00
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