19 UNIVERSAL SERIAL INTERFACE WITH LCD INTERFACE (USIL)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
19-3
Pin name
USIL mode
Signal name
I/O
Function
LCD_D[7:0] UART
–
–
Not used
SPI master
–
–
SPI slave
–
–
I
2
C master
–
–
I
2
C slave
–
–
LCD SPI
–
–
LCD parallel
lcdp_da[7:0] I/O 8-bit data input/output pins
Inputs/outputs 8-bit parallel data from/to the LCD driver/panel.
*
When USIL is configured to I
2
C master or slave mode, either the USIL_DI pin or the USIL_CS pin can be used as
the data input/output pin. Note, however, that both the USIL_DI and USIL_CS pins cannot be used as the data in-
put/output pin simultaneously.
Note: Use a GPIO port to output the slave select signal when USIL is configured to SPI master mode.
The USIL input/output pins (USIL_DI, USIL_DO, USIL_CK, USIL_CS, LCD_D[7:0]) are shared with I/O ports
and are initially set as general-purpose I/O port pins. The pin functions must be switched using the port function
select bits to use the general purpose I/O port pins as USIL input/output pins.
For detailed information on pin function switching, see the “I/O Ports (GPIO)” chapter.
USIL Clock Sources
19.3
Operating clock
The USIL uses PCLK2 as the operating clock. Therefore, PCLK2 must be supplied from the CMU before start-
ing the USIL including setting the control registers. For more information on the PCLK2 supply, refer to the
“Clock Management Unit (CMU).”
Transfer clock
When the USIL is configured to a UART, SPI master (normal mode), I
2
C master, LCD SPI, or LCD parallel
interface, the source clock for transfer is supplied by the 8-bit programmable timer (T8 Ch.3). Program T8 Ch.3
according to the transfer rate and enable supplying the source clock to the USIL module. The USIL module di-
vides the source clock to generate the transfer clock (or sampling clock). Be aware that the division ratio in the
USIL depends on the interface mode.
When the USIL is configured to an SPI master (fast mode), PCLK2 is used as the source clock.
When the USIL is configured to an SPI slave or I
2
C slave device, the transfer clock is supplied from the exter-
nal master device. However, SPI slave mode uses PCLK2 and I
2
C slave mode uses the T8 Ch.3 output clock to
generate the sampling signal.
3.1 USIL Clocks
Table 19.
Clock
Interface mode
Clock source
Operating clock
UART
PCLK2
SPI master
PCLK2
SPI slave
PCLK2
I
2
C master
PCLK2
I
2
C slave
PCLK2
LCD SPI
PCLK2
LCD parallel
PCLK2
Transfer/sampling
clock source
(division ratio in
USIL)
UART
T8 Ch.3 (f
SOURCE
/8)
SPI master
Normal mode: T8 Ch.3 (f
SOURCE
/2)
Fast mode:
PCLK2 (f
PCLK2
)
SPI slave
PCLK2 (f
PCLK2
/4) for sampling
I
2
C master
T8 Ch.3 (f
SOURCE
/8)
I
2
C slave
T8 Ch.3 (f
SOURCE
) for sampling
LCD SPI
T8 Ch.3 (f
SOURCE
/2)
LCD parallel
T8 Ch.3 (f
SOURCE
)
UART mode, I
2
C master mode
bps = f
SYS_CLK
×
DF / {(TR + 1)
×
8 + TFMD}
TR = (f
SYS_CLK
×
DF / bps - TFMD - 8) / 8