INTERNAL SPECIFICATIONS

 

 

Table 4-16 Serial port operation modes

 

 

 

 

 

SM0

SM1

Mode

Function

Baud rate

 

 

 

 

 

0

0

0

I/O extension

1/12 FOSC

 

 

 

 

 

0

1

1

10-bit frame UART

Vareable

 

 

 

 

 

1

0

2

11-bit frame UART

1/32 FOSC or 1/64 FOSC

 

 

 

 

 

1

1

3

11-bit frame UART

Vareable

 

 

 

 

 

Note: FOSC denotes frequency of fundamental oscillator (XTAL1·2).

4.6.2.2 SBUF (serial port buffer register)

SBUF is an 8-bit special function register used to store transmitting and receiving data. Although the SBUF is specified by the same data address 99H for both writing and reading, physically separate registers are specified. That is, the sending circuit SBUF is specified by instructions where SBUF is used as a destination operand, and the receiving circuit SBUF is specified by instructions where SBUF is used as a source operand.

4.6.2.3 TCLK

TCLK controls selection of the baud rate clock source for the transmitting circuit when in mode 1 or 3.

The timer/counter 2 overflow becomes the transmitting circuit baud rate clock source when TCLK is set in mode 1 or 3. And the timer/counter 1 overflow becomes the transmitting circuit baud rate clock source if TCLK is cleared.

TCLK has no effect on the baud rate clock source when in mode 0 or 2. TCLK is located at bit 4 of T2CON (timer/counter 2 control register) specified by data address 0C8H. This bit can also be specified by bit address 0CCH.

4.6.2.4 RCLK

RCLK controls selection of the baud rate clock source for the receiving circuit when in mode 1 or 3.

The timer/counter 2 overflow becomes the receiving circuit baud rate clock source when RCLK is set in mode 1 or 3. And the timer/counter 1 overflow becomes the receiving circuit baud rate clock source if RCLK is cleared.

RCLK has no effect on the baud rate clock source when in mode 0 or 2. RCLK is located at bit 5 of T2CON (timer/counter 2 control register) specified by data address 0C8H. This bit can also be specified by bit address 0CDH.

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Sonic Alert msm85c154hvs, msm83c154s Sbuf serial port buffer register, Tclk, Rclk, Serial port operation modes, SM0 SM1