Registers Controlling Port Function; Format Of Port Mode Register - NEC switch User Manual

4.3 Registers Controlling Port Function

The following three types of registers control the ports.
• Port mode registers (PM0, PM1, PM2, PM4)
• Pull-up resistor option register (PU0)
• Port output mode registers (POM0, POM1)
(1) Port mode registers (PM0, PM1, PM2, PM4)
These registers are used to set port input/output in 1-bit units.
The port mode registers are independently set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets registers to FFH.
When port pins are used as alternate-function pins, set the port mode register and output latch according to
Table 4-3.
Caution As P26 can be used as an external interrupt 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.
Symbol 7 6 5
PM0
PM07 PM06 PM05
PM1 PM17 PM16 PM15 PM14 PM13 PM12 PM11 PM10
PM2 1 PM26 PM25
PM4 PM47 PM46 PM45 PM44 PM43 PM42 PM41 PM40
PMmn
0 Output mode (output buffer on)
1 Input mode (output buffer off)
CHAPTER 4 PORT FUNCTIONS
Figure 4-11. Format of Port Mode Register
4 3 2 1
PM04 PM03 PM02 PM01 PM00
PM24 PM23 PM22 PM21 PM20
Pmn pin input/output mode selection
User's Manual U12978EJ3V0UD
0 Address After reset
FF20H FFH
FF21H FFH
FF22H FFH
FF24H FFH
R/W
R/W
R/W
R/W
R/W
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