SERIAL I/O (SIO) PORT

SPx_BAUD (Continued)

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

 

 

 

 

 

 

 

 

 

 

 

 

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:

 

 

 

 

 

BAUD_VALUE =

FXTAL1

1

or

BCLKx

 

 

Baud----------------Rate--------------×-----2--

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

 

 

Asynchronous modes 1, 2, and 3:

 

 

 

 

 

BAUD_VALUE =

FXTAL1

1

or

BCLKx

 

 

Baud----------------Rate--------------×-----16-----

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

 

 

 

 

 

 

 

Synchronous mode 4 (SCLKx# output):

 

 

 

 

BAUD_VALUE =

FXTAL1

1

 

 

 

 

Baud----------------Rate--------------×-----4--

 

 

 

 

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 7-7. Serial Port x Baud Rate (SPx_BAUD) Register (Continued)

7-13

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Intel 8XC196MC, 8XC196MD, 8XC196MH manual Baudvalue =, Bclk