19 UNIVERSAL SERIAL INTERFACE WITH LCD INTERFACE (USIL)
S1C33L26 TECHNICAL MANUAL
Seiko Epson Corporation
19-25
Set the command bit (LPCMD/USIL_LPCFG register) value before writing to LPRD. The command bit value
set is output from the USIL_DI pin immediately after it is written to the register. Then it loads the LCD_D[7:0]
pin status to the read (receive data) buffer (RD[7:0]/USIL_RD register). LPRD retains 1 until the read data is
loaded to the read buffer.
When LCD_D[7:0] is loaded to the read buffer, the read buffer full flag (LPRDIF/USIL_LPIF register) is set to
1 indicating that the buffered data can be read out. LPRDIF is an interrupt flag. An interrupt or DMA request
can be generated when this flag is set to 1 (see Section 19.7). Read data from the read buffer using this interrupt
or DMA. The read buffer size is 1 byte, therefore the buffered data must be read before starting the subsequent
data reading. LPRDIF is reset by writing 1.
The LPBSY flag indicates the parallel interface status. This flag switches to 1 when LPRD is set to 1 and re-
verts to 0 after the read cycle is completed. Read this flag to check whether the parallel interface circuit is oper-
ating or at standby.
Note: Once a triggered read cycle is completed, data is stored in the read buffer and LPRDIF switches
to high. After that read data from the read buffer before issuing the next read trigger. Otherwise, a
subsequent read operation will not be started.
PCLK2
T8 output clock
LPRD
LPBSY
(Read trigger)
LPRDIF
USIL_CS (lcdp_cs)
USIL_CK (lcdp_rd)
USIL_DI (lcdp_a0)
LCD_D[7:0]
RD[7:0]
Interrupt
data 1
data 2
LPCMD value
Read data 1
Read data 2
(LPWT[3:0] = 0x0, LPST[1:0] = 0x0, LPHD[1:0] = 0x0)
5.5.2 Single Read Timing Chart (LCD parallel mode)
Figure 19.
Successive data read
The LCD parallel interface supports a successive data read function. By issuing a read trigger (writing 1 to
LPRD) after setting the successive read enable bit (LPSRDEN/USIL_LPCFG register) to 1, the LCD parallel
interface repeats data reading from the LCD driver/panel while LPSRDEN is 1 (reading the read buffer issues
the next read trigger). When LPSRDEN is set to 0, the LCD parallel interface stops data reading after the read
cycle being currently executed has finished. An interrupt or DMA can be generated in each read cycle (when
data is loaded to the read buffer) similar to the single read operation, use it to read out the read buffer.
Note: After successive data reading has been terminated, there are 2 or 3 data remained in the read
buffer. Be sure to read them as shown in the flow chart (Figure 19.5.5.4).