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8XC196MC, MD, MH USER’S MANUAL
C-50
SPx_BAUD
SP
x
_BAUD
x
= 0–1 (8XC196MH)
Address:
Reset State:
1F84H, 1F8CH
0000H
The serial port baud rate
x
(SP
x
_BAUD) register selects the serial port
x
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 XTAL1 and 0001H when using BCLK
x
. In synchronous mode 0,
the minimum BAUD_VALUE is 0001H for transmissions and 0002H for receptions. In synchronous
mode 4, the minimum BAUD_VALUE is 0001H for both transmissions and receptions.
15 8
8XC196MH 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 = input frequency on the XTAL1 pin (internal source)
14:0 BV14:0 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
Synchronous mode 4 (SCLK
x
# output):
†
For mode 0 receptions, the BAUD_VALUE must be 0002H or greater.
Otherwise, the resulting data in the receive shift register will be incorrect.
BAUD_VALUE
F
XTAL1
Baud Rate 2×
--------------------------------------
1–=
BCLK
x
Baud Rate
----------------------------
BAUD_VALUE
F
XTAL1
Baud Rate 16×
-----------------------------------------
1–=
BCLK
x
Baud Rate 8×
--------------------------------------
BAUD_VALUE
F
XTAL1
Baud Rate 4×
--------------------------------------
1–=