Serial Communication Interface (S12SCIV5)
S12XS Family Reference Manual, Rev. 1.13
Freescale Semiconductor
427
shows a burst of noise near the beginning of the start bit that resets the RT clock. The sample
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.
Figure 14-26. Start Bit Search Example 5
In
, a noise burst makes the majority of data samples RT8, RT9, and RT10 high. This sets the
noise flag but does not reset the RT clock. In start bits only, the RT8, RT9, and RT10 data samples are
ignored.
Figure 14-27. Start Bit Search Example 6
14.4.6.4
Framing Errors
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.
Reset RT Clock
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
2
RT
3
RT
4
RT
7
RT
6
RT
5
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
Samples
RT Clock
RT Clock Count
Start Bit
RXD
1
1
1
1
1
0
1
0
LSB
1
1
1
1
1
0
0
0
0
0
0
0
0
No Start Bit Found
Reset RT Clock
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
1
RT
2
RT
3
RT
4
RT
7
RT
6
RT
5
R
T10
RT
9
RT
8
R
T14
R
T13
R
T12
R
T11
R
T15
R
T16
RT
1
RT
2
RT
3
Samples
RT Clock
RT Clock Count
Start Bit
RXD
1
1
1
1
1
0
0
0
LSB
1
1
1
1
0
1
1
0
Содержание MC9S12XS128
Страница 4: ...S12XS Family Reference Manual Rev 1 13 4 Freescale Semiconductor ...
Страница 58: ...Device Overview S12XS Family S12XS Family Reference Manual Rev 1 13 58 Freescale Semiconductor ...
Страница 150: ...Memory Mapping Control S12XMMCV4 S12XS Family Reference Manual Rev 1 13 150 Freescale Semiconductor ...
Страница 168: ...Interrupt S12XINTV2 S12XS Family Reference Manual Rev 1 13 168 Freescale Semiconductor ...
Страница 194: ...Background Debug Module S12XBDMV2 S12XS Family Reference Manual Rev 1 13 194 Freescale Semiconductor ...
Страница 364: ...Periodic Interrupt Timer S12PIT24B4CV1 S12XS Family Reference Manual Rev 1 13 364 Freescale Semiconductor ...
Страница 396: ...Pulse Width Modulator S12PWM8B8CV1 S12XS Family Reference Manual Rev 1 13 396 Freescale Semiconductor ...
Страница 506: ...Voltage Regulator S12VREGL3V3V1 S12XS Family Reference Manual Rev 1 13 506 Freescale Semiconductor ...
Страница 736: ...Ordering Information S12XS Family Reference Manual Rev 1 13 736 Freescale Semiconductor ...
Страница 737: ......