CHAPTER 12 PORT FUNCTIONS
User’s Manual U12688EJ4V0UM00
407
12.3.16 Port X
Port X is a 3-bit input/output port that can be set to input or output in 1-bit units.
Address
FFFFF41AH
7
PX7
PX
6
PX6
5
PX5
4
—
3
—
2
—
1
—
0
—
After reset
Undefined
Bit Position
Bit Name
Function
7 to 5
PXn (n = 7 to 5)
Port X
Input/output port
In addition to their function as port pins, the port X pins can also operate as DRAM refresh request signal output,
wait control input, and internal system clock output in the control mode. Lower 5 bits of port X are always undefined in
the case of 8-bit access.
(1) Operation in control mode
Port
Control Mode
Remark
Block Type
PX5
REFRQ
DRAM refresh request signal output
A
PX6
WAIT
Wait control input
L
Port X
PX7
CLKOUT
Internal system clock output
A
(2) Input/output mode/control mode setting
Port X input/output mode setting is performed by means of the port X mode register (PMX), and control mode
setting is performed by means of the port X mode control register (PMCX).
(a) Port X mode register (PMX)
This register is write-only, in 8-bit units. However, the lower 5 bits are fixed at 1 by hardware, so even if 0
is written, it is disregarded.
Address
FFFFF43AH
7
PMX7
PMX
6
PMX6
5
PMX5
4
1
3
1
2
1
1
1
0
1
After reset
FFH
Bit Position
Bit Name
Function
7 to 5
PMXn
(n = 7 to 5)
Port Mode
Sets PXn pin in input/output mode.
0: Output mode (output buffer ON)
1: Input mode (output buffer OFF)
Caution Do not change the port mode using a bit manipulation instruction (CLR1, NOT1, SET1, TST1).
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