Port Function Control Registers - NEC mPD780344 Series User Manual

4.3 Port Function Control Registers

The following four types of registers control the ports.
• Port mode registers (PM0, PM2 to PM4, PM7 to PM11)
• Pull-up resistor option registers (PU0, PU2 to PU4)
• Memory expansion register (MEM)
• Pin function switching registers (PF8 to PF11)
(1) Port mode registers (PM0, PM2 to PM4, PM7 to PM11)
These registers are used to set port input/output in 1-bit units.
PM0, PM2 to PM4, and PM7 to PM11 are independently set by a 1-bit or 8-bit memory manipulation instruction.
RESET input sets the values of these registers to FFH.
Cautions 1. The P10 to P17 pins are input-only pins.
2. As port 0 has an alternate function as an 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. If a pin of ports 0, 2, and 3 is used as an alternate output function, set the output latches
(P0, P2, and P3) to 0.
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CHAPTER 4 PORT FUNCTIONS
User's Manual U15798EJ2V0UD