NEC UPD789026 Series, User Manual

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CHAPTER 4 PORT FUNCTIONS
User's Manual U11919EJ3V0UM00
81
4.3 Port Function Control Registers
The following two types of registers control the ports.
• Port mode registers (PM0 to PM5)
• Pull-up resistor option register (PUO)
(1) Port mode registers (PM0 to PM5)
These registers are used to set port input/output in 1-bit units.
Port mode registers are independently set with a 1-bit or 8-bit memory manipulation instruction.
RESET input sets these 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 port 3 has an alternate function as 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.
Table 4-3. Port Mode Register and Output Latch Settings when Using Alternate Functions
Alternate Function Pin Name
Name Input/Output
PM
××
P
××
P30 INTP0 Input 1
×
P31 INTP1 Input 1
×
INTP2 Input 1
×
P32
CPT2 Input 1
×
P40 to P47
Note
KR0 to KR7 Input 1
×
TI0 Input 1
×
P50
TO0 Output 0 0
P51 TO2 Output 0 0
Note When an alternate function is used, set the key return mode register 00 (KRM00) to 1 (see Section
10.3 (5)).
Caution When Port 2 is used for serial interface pin, the I/O mode and output latch must be set
according to its function. For details of the settings, see Table 9-2.
Remark
×
: Don't care
PM
××
: Port mode register
P
××
: Output latch of port
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