19 UNIVERSAL SERIAL INTERFACE WITH LCD INTERFACE (USIL)
19-22
Seiko Epson Corporation
S1C33L26 TECHNICAL MANUAL
Data reception in I
2
C slave mode
The following describes the data receiving procedure in I
2
C slave mode.
START
END
no
Receive data
Send ACK
Start condition?
Stop condition?
Receive slave address and transfer
direction bit
Address matched?
yes
yes
Send ACK
no
no
yes
5.3.13 I
Figure 19.
2
C Slave Data Receiving Flow Chart
0x0
0x4
0x3
Address
0x3
A6
A5
D7
D6
D5
D4
D3
D2
D1
D0
A4
A3
A2
A1
A0 R/W = 0
ACK
USIL_CK pin (output)
USIL_CK pin (input)
USIL_DI pin (output)
USIL_DI pin (input)
ISTGMOD[2:0]
ISTG (write)
ISBSY
ISSTA[2:0]
RD[7:0]
ISIF
Start detection
interrupt
End of reception
interrupt
End of reception
interrupt
Transfer
ACK interrupt
*
1
*
1
*
1
*
1
0x0
*
2
*
2
*
2
0x3
0x4
0x3
(1) Start condition
→
Data reception
NAK
0x4
0x4
0x3
0x3
D7
D6
D5
D4
D3
D2
D1
D0
ACK
USIL_CK pin (output)
USIL_CK pin (input)
USIL_DI pin (output)
USIL_DI pin (input)
ISTGMOD[2:0]
ISTG (write)
ISBSY
ISSTA[2:0]
RD[7:0]
ISIF
Stop detection
interrupt
*
1
*
1
*
1
*
1
End of reception
interrupt
Transfer
NAK interrupt
Transfer
ACK interrupt
Received data (n - 1)
Received data n
*
2
*
2
*
2
*
2
0x3
0x4
0x1
0x4
(2) Data reception
→
Stop condition
*
1 When the USIL_CK input is detected as low after the operation selected by ISTGMOD[2:0] has finished, the USIL
I
2
C slave controller pulls down the USIL_CK pin to low to places the external I
2
C master into wait state. This pull-
down is canceled to release the I
2
C master from wait state when the subsequent operation is triggered by ISTG.
*
2 When ISIF is cleared via software, ISSTA[2:0] is also cleared to 0x0.
5.3.14 I
Figure 19.
2
C Slave Data Receiving Timing Chart
Note: The timing chart above shows a basic transfer operation that does not include an actual I
2
C trans-
fer procedure. See “Receiving control byte in I
2
C slave mode” in “19.9 Precautions.”