SIC63616-(Rev. 1.0) NO. P122
3240-0412
The serial interface input/output ports are shared with the I/O port (P20–P23), and they are configured
to the I/O port terminals at initial reset. When using these terminals for the serial interface, switch the
function with software as described above. At least ESIF must be set to 1.
The switch operation automatically sets the input/output direction of the terminals. It is not necessary to
set the I/O port control registers. The I/O control registers and data registers of the I/O ports can be used
as general-purpose registers that do not affect the terminal status. However, the pull-up control registers
and input interface select registers of the I/O ports are effective when they are used for the serial inputs.
4.10.3 Mask option
Since the input/output terminals of the serial interface are shared with the I/O ports (P20–P23), the mask
option that selects the terminal specification for the I/O port is also applied to the serial interface terminals.
Output specification
The output specification of the SOUT, SCLK (in master mode) and SRDY (in slave mode) terminals that
are used as the serial interface outputs is respectively selected by the mask options for P21, P20 and P23.
Either complementary output or P-channel open drain output can be selected as the output specifica-
tion. However, when P-channel open drain output is selected, do not apply voltage exceeding the power
supply voltage to the terminal.
Pull-down resistor
The pull-down resistor for the SIN, SCLK (in slave mode) and SS (in SPI slave mode) terminals that
are used as inputs can be incorporated by the mask options for P22, P20 and P23. When the pull-down
resistor is not used, take care that a floating status does not occur.
When a pull-down resistor is incorporated at the serial input terminal, the pull-down resistor should be
enabled/disabled using the pull-down control register of the I/O port.
SIN terminal: PUL22 register
SCLK terminal: PUL20 register
SS terminal:
PUL23 register
Refer to Section 4.5, "I/O Ports", for controlling the pull-down resistors.