Intel 8XC196NP User Manual
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.
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)
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.
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.
an external source.
0 = signal on the T1CLK pin (external source)
1 = internal operating frequency (f)
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.
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
×
--------------------------------------