UPD784938 Datasheet, PDF (134/733 Pages) NEC – 16-Bit Single-Chip Microcontrollers

CHAPTER 6 PORT FUNCTIONS
(3) When specified as control signal input/output
P12 to P14 (by setting (to 1) bits of the port 1 mode control register (PMC1)) can be used as control signal inputs or outputs
bit-wise irrespective of the setting of the port 1 mode register (PM1). When a pin is used as a control signal, the control
signal status can be seen by executing a port read instruction.
Figure 6-17. Control Specification
Control
(output)
Control (input)
PM1n = 0
P1n
n = 2 to 4
RD
Internal
bus
PM1n = 1
(a) When port is control signal output
When the port 1 mode register (PM1) is set (to 1), the control signal pin level can be read by executing a port read
instruction.
When PM1 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
When the port 1 mode register (PM1) is set (to 1), control signal pin level can be read by executing a port read
instruction.
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Preliminary User’s Manual U13987EJ1V0UM00