12 UART (UART3)
S1C17M20/M21/M22/M23/M24/M25
Seiko Epson Corporation
12-3
TECHNICAL MANUAL (Rev. 1.0)
12.3.2 Clock Supply in SLEEP Mode
When using the UART3 during SLEEP mode, the UART3 operating clock CLK_UART3_
n
must be configured so
that it will keep supplying by writing 0 to the CLGOSC.
xxxx
SLPC bit for the CLK_UART3_
n
clock source.
12.3.3 Clock Supply in DEBUG Mode
The CLK_UART3_
n
supply during DEBUG mode should be controlled using the UA
n
CLK.DBRUN bit.
The CLK_UART3_
n
supply to the UART3 Ch.
n
is suspended when the CPU enters DEBUG mode if the UA
n
CLK.
DBRUN bit = 0. After the CPU returns to normal mode, the CLK_UART3_
n
supply resumes. Although the UART3
Ch.
n
stops operating when the CLK_UART3_
n
supply is suspended, the output pin and registers retain the status
before DEBUG mode was entered. If the UA
n
CLK.DBRUN bit = 1, the CLK_UART3_
n
supply is not suspended
and the UART3 Ch.
n
will keep operating in DEBUG mode.
12.3.4 Baud Rate Generator
The UART3 includes a baud rate generator to generate the transfer (sampling) clock. The transfer rate is determined
by the UA
n
MOD.BRDIV, UA
n
BR.BRT[7:0], and UA
n
BR.FMD[3:0] bit settings. Use the following equations to
calculate the setting values for obtaining the desired transfer rate.
CLK_UART3 CLK_UART3
bps = —————————
BRT = BRDIV
×
(
—————— - FMD
)
- 1 (Eq. 12.1)
BRT + 1
bps
———— + FMD
BRDIV
Where
bps:
Transfer rate [bit/s]
CLK_UART3: UART3 operating clock frequency [Hz]
BRDIV:
Baud rate division ratio (1/16 or 1/4)
*
Selected by the UA
n
MOD.BRDIV bit
BRT: UA
n
BR.BRT[7:0] setting value (0 to 255)
FMD: UA
n
BR.FMD[3:0] setting value (0 to 15)
For the transfer rate range configurable in the UART3, refer to “UART Characteristics, Transfer baud rates U
BRT1
and U
BRT2
” in the “Electrical Characteristics” chapter.
12.4 Data Format
The UART3 allows setting of the data length, stop bit length, and parity function. The start bit length is fixed at one
bit.
Data length
With the UA
n
MOD.CHLN bit, the data length can be set to seven bits (UA
n
MOD.CHLN bit = 0) or eight bits
(UA
n
MOD.CHLN bit = 1).
Stop bit length
With the UA
n
MOD.STPB bit, the stop bit length can be set to one bit (UA
n
MOD.STPB bit = 0) or two bits
(UA
n
MOD.STPB bit = 1).
Parity function
The parity function is configured using the UA
n
MOD.PREN and UA
n
MOD.PRMD bits.
Table 12.4.1 Parity Function Setting
UAnMOD.PREN bit
UAnMOD.PRMD bit
Parity function
1
1
Odd parity
1
0
Even parity
0
*
Non parity