8XC196MC, MD, MH USER’S MANUAL

SPx_BAUD

SPx_BAUD

Address:

1F84H, 1F8CH

x = 0–1 (8XC196MH)

Reset State:

0000H

The serial port baud rate x (SPx_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 BCLKx. 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.

8XC196MH

15

CLKSRC

BV14

BV13

BV12

7

 

 

 

 

 

 

 

BV7

BV6

BV5

BV4

 

 

 

 

8

BV11

BV10

BV9

BV8

 

 

 

0

 

 

 

 

BV3

BV2

BV1

BV0

 

 

 

 

Bit

Bit

Function

 

Number

Mnemonic

 

 

 

 

 

 

 

 

 

 

 

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:

 

 

 

 

 

FXTAL1

1

 

BCLKx

 

 

BAUD_VALUE = Baud----------------Rate--------------×-----2--

or

Baud----------------------------Rate

 

 

Asynchronous modes 1, 2, and 3:

 

 

 

 

 

FXTAL1

1

or

BCLKx

 

 

BAUD_VALUE = ----------------------------------------

Baud-------------------------------------Rate× 8

 

 

Baud Rate × 16

 

 

 

 

Synchronous mode 4 (SCLKx# output):

 

 

 

 

FXTAL1

 

 

 

 

 

BAUD_VALUE = Baud----------------Rate--------------×-----4--

1

 

 

 

 

For mode 0 receptions, the BAUD_VALUE must be 0002H or greater.

 

 

Otherwise, the resulting data in the receive shift register will be incorrect.

 

 

 

 

 

 

C-50

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Intel 8XC196MC, 8XC196MD manual SPxBAUD, 8XC196MH