Energy Meter IC Family Software Instruction Manual

71M652X Software User’s Guide

Revision 1.7 TERIDIAN Proprietary 124 of 138

SM0 SM1 Mode Description Baud Rate

0 0 0 shift register Fclk/12

0 1 1 8-bit UART Variable

1 0 2 9-bit UART Fclk/32 or /64

1 1 3 9-bit UART Variable

Table 6-29: Serial Port 0 Modes

Note: The speed in Mode 2 depends on the SMOD bit in the Special Function Register PCON when SMOD = 1,

Fclk/32.

Serial Interface 1 Modes

The Serial Interface 1 can operate in 2 modes:

SM Mode Description Baud Rate

0 A 9-bit UART variable

1 B 8-bit UART variable

Table 6-30: Serial 1 Modes

Mode A

This mode is similar to Mode 2 and 3 of serial interface 0. 11 bits are transmitted or received: a start bit (0), 8 data bits

(LSB first), a programmable 9

bit, and a stop bit (1). The 9

bit can be used to control the parity of the serial interface:

at transmission, bit tb81 in S1CON is output as the 9th

bit, and at receive, the 9th bit affects rb81 in the Special

Function Register S1CON. The only difference between Mode 3 and A is that in Mode A, only the internal baud rate

generator can be use to specify baud rate.

Mode B

This mode is similar to Mode 1 of serial interface 0. Pin rxd1 serves as an input, and txd1 serves as a serial output. No

external shift clock is used. 10 bits are transmitted: a start bit (always 0), 8 data bits (LSB first), and a stop bit (always

1). On receive, a start bit synchronizes the transmission. 8 data bits are available by reading S1BUF, and the stop bit

sets the flag rb81 in the Special Function Register S1CON. In mode B, the internal baud rate generator specifies the

baud rate.

Serial Interface 1 Control Register (S1CON).

The function of the serial port depends on the setting of the Serial Port Control Register S1CON.

MSB LSB

SM - SM21 REN1 TB81 RB81 TI1 RI1

Table 6-31: The S1CON Register