mpc89x515a Megawin Technology, mpc89x515a Datasheet - Page 26

• Manufacturer Part Number: mpc89x515a
• Description: 8-bit Micro-controller
• Manufacturer: Megawin Technology

Mode2
An 11-bit data is serially transmitted through TXD or received through RXD. The frame data
includes a start bit (0), 8 data bits, a programmable 9th bit and a stop bit (1). On transmit, the
9th data bit comes from TB8 in SFR SCON. On receive, the 9th data bit goes into RB8 in
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 bit 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 bit. This bit is set by the receiver when an invalid stop bit is detected. The FE bit is not
26
SM0/FE
Bit-7
cleared by valid frames, but should be cleared by software. The SMOD0 (PCON.6) bit must be set to
enable access to the FE bit.
{ 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
Bit-6
SM1
Baud Rate (for Mode 3)
Baud Rate (for Mode 2)
Bit-5
SM2
or =
MPC89x515A Data Sheet
=
REN
Bit-4
=
(Timer-2 overflow rate)
2
SMOD
32
2
Bit-3
TB8
16
64
SMOD
X
(Timer-1 overflow rate)
Bit-2
RB8
X F
osc
Bit-1
TI
Bit-0
RI
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