20 GENERAL-PURPOSE SERIAL INTERFACE (FSIO)
20-14
Seiko Epson Corporation
S1C33L26 TECHNICAL MANUAL
A 1/16 division ratio is selected by writing 0 to DIVMD/FSIO_IRDA
x
register, and a 1/8 ratio is selected
by writing 1.
Note: DIVMD becomes indeterminate at initial reset, so be sure to reset it in the software. Settings of
this bit are valid only in the asynchronous mode (and when using the IrDA interface).
For receiving
SIN
x
SIO_CLK
Sampling clock
Sampling of start bit
Start bit
D0
1
8
1
8
8
×
SIO_CLK
16
×
SIO_CLK
Sampling of D0 bit
7.2.1 Sampling Clock for Asynchronous Receive Operation (when 1/16 division is selected)
Figure 20.
Each bit data is sampled in the timing shown in Figure 20.7.2.1. When the SIN
x
input signal is detected as
a low level at the rising edge of SIO_CLK, sampling for the start bit is performed 8
×
SIO_CLK (4
×
SIO_
CLK when 1/8 division is selected) after that point. If a low level is not detected in the sampling for the
start bit, the interface aborts the subsequent samplings and returns to the start bit detection phase (in this
case no error occurs). When the SIN
x
input signal is low at the start bit sampling, subsequent bit data is
sampled in 16
×
SIO_CLK cycles (8
×
SIO_CLK cycles when 1/8 division is selected).
For transmitting
SIO_CLK
Sampling clock
SOUT
x
Start bit
D0
1
8
16
16
×
SIO_CLK
7.2.2 Sampling Clock for Asynchronous Transmit Operation (when 1/16 division is selected)
Figure 20.
During transmission, each bit data is output from the SOUT
x
pin in 16
×
SIO_CLK cycles (8
×
SIO_CLK
cycles when 1/8 division is selected).
Setting the data format
In the asynchronous mode, the data length is 7 or 8 bits as determined by the transfer mode set. The start bit is
fixed at 1.
The stop and parity bits can be configured as shown in the Table 20.7.2.1 using the control bits listed below.
Stop bit selection:
STPB/FSIO_CTL
x
register
Parity enable:
EPR/FSIO_CTL
x
register
Parity mode selection: PMD/FSIO_CTL
x
register
7.2.1 Stop Bit and Parity Bit Settings
Table 20.
STPB
EPR
PMD
Stop bit
Parity bit
1
1
1
2 bits
Odd
0
2 bits
Even
0
*
2 bits
None
0
1
1
1 bit
Odd
0
1 bit
Even
0
*
1 bit
None
*
PMD settings are ineffective when EPR = 0.
(Default: STPB = EPR = PMD = 0)