UPD75518 NEC, UPD75518 Datasheet - Page 49

• Manufacturer Part Number: UPD75518
• Description: 4 BIT SINGLE-CHIP MICROCOMPUTER
• Manufacturer: NEC

(3) Operation of digital I/O ports
When a 1-bit test instruction,
4-, or 8-bit instruction is
executed
When a 4-, 8-bit output
instruction is executed
When a 1-bit output
instruction
When an instruction is executed, the operation of the port and pins depends on the I/O mode setting, as
listed in Table 4-3.
Note Instruction such as SET1 PORTn.bit or CLR1 PORTn.bit
Note
is executed
Table 4-3 I/O Port Operations by I/O Instructions
Input mode
Receives data on certain pins.
Transfers data in the accumulator to
the output latch.
The contents of the output latch are
undefined.
[Output buffer is off]
corresponding bit in
the mode register is 0
Receives the contents of the output
latch.
Outputs data in the accumulator to
output pins.
Changes the output pin state
according to the instruction.
Output mode corresponding bit in
[Output buffer is on]
the mode register is 1
PD75518(A)
49