71M6511/71M6511H
Single-Phase Energy Meter IC
DATA SHEET
AUGUST 2007
The 71M6511 has several UART-related registers, which can be read and written. All UART transfers are programmable for
parity enable, parity, 2 stop bits/1 stop bit and XON/XOFF options for variable communication baud rates from 300 to 38400
bps. Table 13 shows how the baud rates are calculated. Table 14 shows the selectable UART operation modes.
Using Timer 1
Using Internal Baud Rate Generator
2smod * fCKMPU/ (384 * (256-TH1))
2smod * fCKMPU/(64 * (210-S0REL))
fCKMPU/(32 * (210-S1REL))
Serial Interface 0
Serial Interface 1
N/A
Note: S0REL and S1REL are 10-bit values derived by combining bits from the respective timer reload registers. SMOD is the
SMOD bit in the SFR PCON. TH1 is the high byte of timer 1.
Table 13: Baud Rate Generation
UART 0
UART 1
Start bit, 8 data bits, parity, stop bit, variable
Mode 0
Mode 1
Mode 2
Mode 3
N/A
baud rate (internal baud rate generator)
Start bit, 8 data bits, stop bit,
variable baud rate (internal baud
rate generator or timer 1)
Start bit, 8 data bits, parity, stop bit,
fixed baud rate 1/32 or 1/64 of fCKMPU
Start bit, 8 data bits, parity, stop bit,
variable baud rate (internal baud
rate generator or timer 1)
Start bit, 8 data bits, stop bit, variable baud rate
(internal baud rate generator)
N/A
N/A
Table 14: UART Modes
Parity of serial data is available through the P flag of the accumulator. Seven-bit serial modes with parity, such as those used
by the FLAG protocol, can be simulated by setting and reading bit 7 of 8-bit output data. Seven-bit serial modes without parity
can be simulated by setting bit 7 to a constant 1. 8-bit serial modes with parity can be simulated by setting and reading the 9th
bit, using the control bits TB80 (S0CON.3) and TB81 (S1CON.3) in the S0COn and S1CON SFRs for transmit and RB81
(S1CON.2) for receive operations. SM20 (S0CON.5) and SM21 (S1CON.5) can be used as handshake signals for inter-pro-
cessor communication in multi-processor systems.
Serial Interface 0 Control Register (S0CON).
The function of the UART0 depends on the setting of the Serial Port Control Register S0CON.
MSB
SM0
LSB
RI0
SM1
SM20
REN0
TB80
RB80
TI0
Table 15: The S0CON Register
Page: 22 of 95
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