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13 SeRial inTeRFaCe
The serial interface input/output ports are shared with the I/O port (P30–P33), 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 are ineffective. However, the pull-up
control registers of the I/O ports are effective when they are used for the serial inputs.
13.3
Mask Option
Since the input/output terminals of the serial interface are shared with the I/O ports (P30–P33), 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 P31, P30 and P33. Either comple-
mentary output or P-channel open drain output can be selected as the output specification. 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 resistors 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 P32, P30 and P33. When the pull-down resistor is not used,
take care that a floating status does not occur.
Pull-down control when pull-down resistor is incorporated
When a pull-down resistor is incorporated at the serial input terminal, the pull-down resistor should be en-
abled/disabled using the pull-down control register of the I/O port.
SIN terminal:
PUL32 register
SCLK terminal: PUL30 register
SS terminal:
PUL33 register
Refer to the "I/O Ports" chapter for controlling the pull-down resistors.
13.4
Operating Mode of Serial interface
The serial interface supports three operating modes: master mode, slave mode and SPI slave mode.
Master mode
Master mode is provided to use the S1C63004/008/016 as the master device for serial transfer. In this mode,
the serial interface uses the internal clock supplied from the clock manager as the synchronous clock for serial
transfer. The synchronous clock is also output from the SCLK terminal to the slave device. The ready signal sent
from the slave device should be input through an I/O port (in input mode) and it should be read with software to
control data transfer.
The S1C63004/008/016 set to master mode is also used as an SPI master device. The SS (Slave Select) signal
should be output by controlling an I/O port (in output mode) with software.
Slave mode
Slave mode is provided to use the S1C63004/008/016 as a slave device for serial transfer. In this mode, the se-
rial interface inputs the synchronous clock that is sent by the external master device from the SCLK terminal to
perform serial transfer. For the external master device to control data transfer, the serial interface can output a
ready signal indicating that it is ready to transfer from the SRDY terminal by hardware control.
13-2
Seiko epson Corporation
S1C63003/004/008/016 TeChniCal Manual
(Rev. 1.1)
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