NEC mPD780852 Series, Preliminary User'S Manual

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CHAPTER 4 PORT FUNCTIONS
Preliminary User’s Manual U14581EJ3V0UM00
4.3 Port Function Control Registers
The following two types of registers control the ports.
• Port mode registers (PM0, PM2 to PM6, PM8, PM9)
• Pull-up resistor option register (PU0)
(1) Port mode registers (PM0, PM2 to PM6, PM8, PM9)
These registers are used to set port input/output in 1-bit units.
PM0, PM2 to PM6, PM8, and PM9 are independently set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets these registers to FFH.
When a port pin is used as an alternate function pin, set the port mode register and output latch corresponding
to the port in accordance with the function to be used.
Cautions 1. Pins P10 to P17 are input-only pins, and pins P20 to P27 and P30 to P37 are output-only
pins.
2. Port 0 has an alternate function as external interrupt request input, when the port function
output mode is specified and the output level is changed, the interrupt request flag is
set. When the output mode is used, therefore, the interrupt mask flag should be set to
1 beforehand.
3. Ports 2 and 3 that can be also used as meter driving PWM signal output pins go into a
high-impedance state when 1 is set to PM2
×
and PM3
×
, respectively.