20 GENERAL-PURPOSE SERIAL INTERFACE (FSIO)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
20-5
Clock-synchronized master mode (SMD[1:0] = 0x0)
In this mode, clock-synchronized 8-bit serial transfers, in which the serial interface functions as the master,
can be performed using the internal clock to synchronize the operation of the internal shift registers.
The synchronizing clock is output from the SCLK
x
pin, enabling an external (slave side) serial input/output
device to be controlled. The #SRDY
x
pin is also used to input a signal that indicates whether the external
serial input/output device is ready to transmit or receive (when ready in a low level).
Clock-synchronized slave mode (SMD[1:0] = 0x1)
In this mode, clock-synchronized 8-bit serial transfers, in which the serial interface functions as a slave, can
be performed using the synchronizing clock that is supplied by an external (master side) serial input/output
device.
The synchronizing clock is input from the SCLK
x
pin for use as the synchronizing clock of the serial inter-
face. In addition, a #SRDY
x
signal indicating whether the serial interface is ready to transmit or receive (when
ready in a low level) is output from the #SRDY
x
pin.
Figure 20.6.1.1 shows an example of how the input/output pins are connected in the clock-synchronized mode.
Data input
Data output
Clock input
Ready output
SIN
x
SOUT
x
SCLK
x
#SRDY
x
SIN
x
SOUT
x
SCLK
x
#SRDY
x
External
serial device
(1) Master mode
(2) Slave mode
S1C33L26
Data input
Data output
Clock output
Ready input
External
serial device
S1C33L26
6.1.1 Example of Connection in Clock-Synchronized Mode
Figure 20.
Clock-synchronized transfer data format
In clock-synchronized transfers, the data format is fixed as shown below.
Data length: 8 bits
Start bit:
None
Stop bit:
None
Parity bit:
None
SCLK
x
Data
D0 D1 D2 D3 D4 D5 D6 D7
LSB
MSB
6.1.2 Clock-Synchronized Transfer Data Format
Figure 20.
Serial data is transmitted and received starting with the LSB.
Setting Clock-Synchronized Interface
20.6.2
When performing clock-synchronized transfers via the serial interface, the following settings must be made before
data transfer is actually begun:
1. Setting input/output pins
2. Setting the interface mode
3. Setting the transfer mode
4. Setting the clocks
5. Setting the receive FIFO level
6. Setting interrupts and DMA
The following explains the content of each setting. For details on interrupt/DMA settings, refer to Section 20.9,
“FSIO Interrupts and DMA.”
Note: Always make sure the serial interface is inactive (TXEN/FSIO_CTL
x
register and RXEN/FSIO_
CTL
x
register = 0) before these settings are made. A change of settings during operation may
cause a malfunction.