mc9s12e256 Freescale Semiconductor, Inc, mc9s12e256 Datasheet - Page 268

• Manufacturer Part Number: mc9s12e256
• Description: Hcs12 Microcontrollers 16-bit Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Chapter 8 Serial Communication Interface (SCIV4)
Figure 8-20
after the reset is low but is not preceded by three high samples that would qualify as a falling edge.
Depending on the timing of the start bit search and on the data, the frame may be missed entirely or it may
set the framing error flag.
In
noise flag but does not reset the RT clock. In start bits only, the RT8, RT9, and RT10 data samples are
ignored.
8.4.5.4
If the data recovery logic does not detect a logic 1 where the stop bit should be in an incoming frame, it
sets the framing error flag, FE, in SCI status register 1 (SCISR1). A break character also sets the FE flag
because a break character has no stop bit. The FE flag is set at the same time that the RDRF flag is set.
268
RT CLOCK COUNT
RT CLOCK COUNT
RESET RT CLOCK
RESET RT CLOCK
Figure
RT CLOCK
RT CLOCK
SAMPLES
SAMPLES
8-21, a noise burst makes the majority of data samples RT8, RT9, and RT10 high. This sets the
shows a burst of noise near the beginning of the start bit that resets the RT clock. The sample
RXD
RXD
Framing Errors
1
1
1
1
1
1
1
1
1
1
Figure 8-20. Start Bit Search Example 5
Figure 8-21. Start Bit Search Example 6
1
1
MC9S12E256 Data Sheet, Rev. 1.08
1
1
1
1
1
1
0
0
0
0
1
0
START BIT
START BIT
1
0
0
1
NO START BIT FOUND
0
0
0
1
0
0
0
Freescale Semiconductor
0
0
LSB
LSB