DS89C420-QCL Datasheet, PDF (121/139 Pages) Maxim Integrated Products – Ultra-High-Speed Flash Microcontroller User’s Guide

Ultra-High-Speed Flash
Microcontroller User’s Guide
Mode 3
Mode 3 has the same operation as mode 2, except for the baud-rate source. As shown in Figure 12-4, mode 3 can use timer 1 or 2 for
serial port 0 and timer 1 for serial port 1. The bit shifting and protocol are the same.
TIMER 1
OVERFLOW
TIMER 2
OVERFLOW
SBUF
TRANSMIT SHIFT REGISTER
S0
P3.1
LATCH
TXD
PIN
DIVIDE-
BY-2
0 ^{SMOD_0 =}
PCON.7
1
OR
SMOD_1 =
WDCON.7
01
TCLK =
T2CON.4
RCLK =
T2CON.5 _{0 1}
1
TB8 =
SCONx.3
LDSBUF
RDSBUF
DIVIDE-
BY-16
LOAD
SERIAL
BUFFER
BAUD
CLOCK
RESET
SHIFT
READ
SERIAL
BUFFER
LOAD
0
DATA BUS
SBUF
RD RECEIVE DATA BUFFER WR
RB8 =
SCONx.3
T1
FLAG =
SCONx.1
R1
FLAG =
SCONx.0
SERIAL
INTERRUPT
SI
RECEIVE SHIFT REGISTER
DIVIDE-
BY-16
BIT
DETECTION
RXD
PIN
TRANSMIT TIMING
LDSBUF
SHIFT
TXD
TI
RECEIVE TIMING
RXD
BIT DETECTOR
SAMPLING
SHIFT
RI
Figure 12-4. Serial Port Mode 3
START D0
D1
D2
D3
D4
D5
D6 D7
TB8 STOP
START D0
D1
D2
D3
D4
D5
D6
D7
RB8 _STOP
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