71m6403 Teridian Semiconductor Corporation, 71m6403 Datasheet - Page 21

• Manufacturer Part Number: 71m6403
• Description: Electronic Trip Unit
• Manufacturer: Teridian Semiconductor Corporation

UART
The 71M6403 includes a UART (UART0) that can be programmed for general purpose communications. A second UART
(UART1) is connected to the optical port, as described in the optical port description.
The UART is a dedicated 2-wire serial interface, which can communicate with an external host processor at up to 38,400 bits/s
(with MPU clock = 1.2288MHz). The operation of each pin is as follows:
RX: Serial input data are applied at this pin. Conforming to RS-232 standard, the bytes are input LSB first. The voltage applied at
RX must not exceed 3.6V.
TX: This pin is used to output the serial data. The bytes are output LSB first.
The 71M6403 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 11 shows how the baud rates are calculated. Table 12 shows the selectable UART operation modes.
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.
Note: 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
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th
bit, using the control bits S0CON3 and S1CON3 in the S0COn and S1CON SFRs.
Serial Interface 0
Serial Interface 1
Mode 0
Mode 1
Mode 2
Mode 3
fixed baud rate 1/32 or 1/64 of f
Start bit, 8 data bits, parity, stop bit,
Start bit, 8 data bits, parity, stop bit,
variable baud rate (internal baud
variable baud rate (internal baud
Start bit, 8 data bits, stop bit,
rate generator or timer 1)
rate generator or timer 1)
2
smod
* f
CKMPU
UART 0
Using Timer 1
N/A
Table 11: Baud Rate Generation
/ (384 * (256-TH1))
©
N/A
2006 TERIDIAN Semiconductor Corporation
Table 12: UART Modes
CKMPU
Start bit, 8 data bits, stop bit, variable baud rate
Start bit, 8 data bits, parity, stop bit, variable
baud rate (internal baud rate generator)
Using Internal Baud Rate Generator
(internal baud rate generator)
2
smod
Electronic Trip Unit
f
CKMPU
* f
CKMPU
UART 1
/(32 * (2
N/A
N/A
/(64 * (2
10
-S1REL))
10
-S0REL))
71M6403
SEPTEMBER 2006
REV 1.0