mpc89x51a Megawin Technology, mpc89x51a Datasheet - Page 25

• Manufacturer Part Number: mpc89x51a
• Description: 8-bit Micro-controller
• Manufacturer: Megawin Technology

Mode2
An 11-bits data is serially transmitted through TXD or received through RXD. The frame data
includes a start bits (0), 8 data bits, a programmable 9
the 9
SCON. The baud rate is programmable, and permitted to be set either 1/32 or 1/64 the
oscillator frequency.
Mode3
Mode 3 is the same as mode 2 except the baud rate is variable.
In all four modes, transmission is initiated by any instruction that uses SBUF as a destination
register. Reception is initiated in mode 0 by the condition RI = 0 and REN = 1. Reception is
initiated in the other modes by the incoming start bits with 1-to-0 transition if REN=1.
There are several SFR related to serial port configuration described as following.
SFR: SCON (Serial Port Control):
{ SM0, SM1 }: Used to set operating mode of the serial port. It is enabled to access by clearing SMOD0.
FE: Frame Error bits. This bits is set by the receiver when an invalid stop bits is detected. The FE bits is
MEGAWIN
SM0/FE
Bits-7
not cleared by valid frames, but should be cleared by software. The SMOD0 (PCON.6) bits must be
set to enable access to the FE bits.
th
data bits comes from TB8 in SFR SCON. On receive, the 9
{ 0, 0 } := set the serial port operate under Mode 0
{ 0, 1 } := set the serial port operate under Mode 1
{ 1, 0 } := set the serial port operate under Mode 2
{ 1, 1 } := set the serial port operate under Mode 3
Bits-6
SM1
Baud Rate (for Mode 3)
Baud Rate (for Mode 2)
Bits-5
SM2
or =
MPC89x51A Data Sheet
=
Bits-4
REN
=
(Timer-2 overflow rate)
2
SMOD
32
Bits-3
2
TB8
16
64
SMOD
X
th
bits and a stop bits (1). On transmit,
(Timer-1 overflow rate)
Bits-2
RB8
X F
osc
th
data bits goes into RB8 in
Bits-1
TI
Bits-0
RI
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