CHAPTER 4 PORT FUNCTIONS
Preliminary User’s Manual U16846EJ1V0UD
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4.2.6 Port 13
Port 13 is a 1-bit output-only port.
Figure 4-13 shows a block diagram of port 13.
Figure 4-13. Block Diagram of P130
RD
Output latch
(P130)
WR
PORT
P130
Internal bus
RD: Read
signal
WR
××
: Write
signal
Remark When reset is effected, P130 outputs a low level. If P130 is set to output a high level before reset is
effected, the output signal of P130 can be dummy-output as the reset signal to the CPU.
4.3 Registers Controlling Port Function
Port functions are controlled by the following three types of registers.
•
Port mode registers (PM0, PM1, PM3, PM12)
•
Port registers (P0 to P3, P12, P13)
•
Pull-up resistor option registers (PU0, PU1, PU3, PU12)
(1) Port mode registers (PM0, PM1, PM3, and PM12)
These registers specify input or output mode for the port in 1-bit units.
These registers can be set by 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 as shown in Table
4-3.