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8-11
SERIAL I/O (SIO) PORT
SP_BAUD
Address:
Reset State:
1FBCH
0000H
The serial port baud rate (SP_BAUD) register selects the serial port baud rate and clock source. The
most-significant bit selects the clock source. The lower 15 bits represent BAUD_VALUE, an unsigned
integer that determines the baud rate.
The maximum BAUD_VALUE is 32,767 (7FFFH). In asynchronous modes 1, 2, and 3, the minimum
BAUD_VALUE is 0000H when using the internal clock source (f)
and 0001H when using T1CLK. In
synchronous mode 0, the minimum BAUD_VALUE is 0001H for transmissions and 0002H for
receptions.
15 8
CLKSRC BV14 BV13 BV12 BV11 BV10 BV9 BV8
7 0
BV7 BV6 BV5 BV4 BV3 BV2 BV1 BV0
Bit
Number
Bit
Mnemonic
Function
15 CLKSRC Serial Port Clock Source
This bit determines whether the serial port is clocked from an internal or
an external source.
0 = signal on the T1CLK pin (external source)
1 = internal operating frequency (f)
14:0 BV14:0 Baud Rate
These bits constitute the BAUD_VALUE.
Use the following equations to determine the BAUD_VALUE for a given
baud rate.
Synchronous mode 0:
†
or
Asynchronous modes 1, 2, and 3:
or
†
For mode 0 receptions, the BAUD_VALUE must be 0002H or greater.
Otherwise, the resulting data in the receive shift register will be incorrect.
Figure 8-7. Serial Port Baud Rate (SP_BAUD) Register
BAUD_VALUE
f
Baud Rate 2×
--------------------------------------
1–=
T1CLK
Baud Rate
----------------------------
BAUD_VALUE
f
Baud Rate 16×
-----------------------------------------
1–=
T1CLK
Baud Rate 8×
--------------------------------------