UPD784938 Datasheet, PDF (152/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 6 PORT FUNCTIONS
(3) When specified as control signal input/output
By setting (to 1) bits of the port 3 mode control register (PMC3), port 3 can be used as control signal input or output bit-wise
irrespective of the setting of the port 3 mode register (PM3). When a pin is used as a control signal, the control signal status
can be seen by executing a port read instruction.
Figure 6-34. Control Specification
Control (input)
Control
(output)
PM3n = 0
P3n
n = 0 to 7
RD
PM3n = 1
Internal bus
(a) When port is control signal output
When the port 3 mode register (PM3) is set (to 1), the control signal pin level can be read by executing a port read
instruction.
When PM3 is reset (to 0), the µPD784938 internal control signal status can be read by executing a port read instruction.
(b) When port is control signal input
Only the port 3 mode register (PM3) is set (to 1), control signal pin levels can be read by executing a port read instruction.
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Preliminary User’s Manual U13987EJ1V0UM00