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10 I/O Ports (P)
10.1 Structure of I/O Port
The S1C17704 contains 28 I/O ports (P0[7:0], P1[7:0], P2[7:0], and P3[3:0]) that can be directed for input or
output with software. Although the I/O pins, except for some I/O ports, are shared with internal peripheral modules,
the pins can be used as general-purpose input/output ports unless they are used for the peripheral modules.
Figure 10.1.1 shows the structure of a typical I/O port.
I/O direction select
Peripheral I/O control
Function select
Schmitt trigger control
The P0 and P1 ports can generate input interrupts.
The P0[3:0] ports can be used as the key-entry reset ports (see Section 5.1.2, "P0 Port Key-Entry Reset," for
details).
Note: Supply PCLK from the clock generator before the I/O ports can be accessed.
Furthermore, a prescaler output clock is required for operating the P0 port chattering filter. Turn
the prescaler on when using the chattering filter.
S1C17704 TECHNICAL MANUAL
Pull-up enable
PxPUy
PxIOy
PxyMUX
Output data
PxOUTy
Peripheral output
PxSMy
Peripheral input
Figure 10.1.1 Structure of I/O Port
EPSON
10 I/O PORTS (P)
V
DD
Pxy
V
SS
10-1
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