CHAPTER 5 PORT FUNCTIONS
158
(3) Pin in control mode
P90 through P93
These pins are automatically used as the RD, LWR, HWR, and ASTB pins when the external memory or I/O is
accessed.
At this time, do not execute an I/O instruction to P90 through P93.
P94
This pin can be used as the WAIT pin, regardless of the setting of the port 9 mode register (PM9), if the PMC94
bit of the port 9 mode control register (PMC9) is set (1). When using P94 as the WAIT pin, the status of the WAIT
pin can be read by executing an instruction that reads the port only when the PM94 bit of PM9 is set (1).
Caution The pin that functions as an input pin in the control mode (P94) may malfunction if the PMC94
bit of the port 9 mode control register (PMC9) is rewritten while the pin is operating. Therefore,
write PMC9 on initializing the system.
5.11.4 Internal pull-up resistor
Port 9 is provided with pull-up resistors. When the port must be pulled up, the number of components and the mounting
area can be reduced by using these internal pull-up resistor.
Whether the internal pull-up resistors are used or not is specified per pin by using the PUO9 bit of the pull-up resistor
option register H (PUOH) and port 9 mode register (PM9).
When the PUO9 bit is 1, the internal pull-up resistor of only the pin specified as follows is valid.
P90 through P93 : Set in input port mode by memory extension mode register (MM) and PM9
P94
: Set in input mode by PM9
Even when P94 is specified as the WAIT pin, specifying its use as a pull-up resistor is valid. In order not to connect the
internal pull-up resistor, either specify the output mode by using PM9 (PM94 = 0), or reset (0) in PUO9.
Figure 5-57. Format of Pull-up Resistor Option Register H (PUOH)
Caution When using P90 through P93 as the RD, LWR, HWR, and ASTB pins, be sure to reset the PUO9 bit to
“0” in order not to connect the internal pull-up resistor.
Remark
Resetting PUOH to 00H is effective for decreasing the current consumption when the STOP mode is set.
0
0
0
0
0
0
PUO9
0
7
6
5
4
3
2
1
0
PUOH
Address : 0FF4FH On reset : 00H R/W
PUO9
0
1
Specifies Pull-up Resistor of Port 9
Not used with port 9
Used with port 9