MSC8113 Reference Manual, Rev. 0
21-16
Freescale Semiconductor
UART
In Figure 21-13, a large burst of noise is perceived as the beginning of a start bit, although the
test sample at RT5 is high. The RT5 sample sets the noise flag. Although this is a worst-case
misalignment of perceived bit time, the RT8, RT9, and RT10 data samples of the next bit are
within the bit time, and data recovery is successful.
Figure 21-14 shows the effect of noise early in the start bit time. Although this noise does not
affect proper synchronization with the start bit time, it does set the noise flag.
Figure 21-15 shows a burst of noise near the beginning of the start bit that causes the start bit not
to be found and resets the RT counter. 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 21-13. Start Bit Search Example 4
Figure 21-14. Start Bit Search Example 5
Reset RT Counter
RT
1
RT
1
RT
1
RT
1
RT
2
RT
3
RT
4
RT
5
RT
6
RT
7
RT
8
RT
9
RT
1
0
RT
1
3
RT
1
2
RT
1
1
RT
1
6
RT
1
5
RT
1
4
RT
4
RT
3
RT
2
RT
1
RT
5
RT
6
RT
7
RT
8
RT
9
Samples
RT Clock
RT Clock Count
Actual Start Bit
URXD
1
0
1
1
1
0 0
0
0
LSB
0
Perceived Start Bit
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
0
RT
9
RT
8
RT
1
4
RT
1
3
RT
1
2
RT
1
1
RT
1
5
RT
1
6
RT
1
RT
2
RT
3
Perceived and Actual Start Bit
1
1
1
1
1
0
0
1
LSB
1
1
1
1
Reset RT Counter
Samples
RT Clock
RT Clock Count
URXD
Summary of Contents for MSC8113
Page 1: ...MSC8113 Reference Manual Tri Core 16 Bit Digital Signal Processor MSC8113RM Rev 0 May 2008 ...
Page 20: ...MSC8113 Reference Manual Rev 0 xx Freescale Semiconductor Contents ...
Page 28: ...MSC8113 Reference Manual Rev 0 xxviii Freescale Semiconductor ...
Page 56: ...MSC8113 Reference Manual Rev 0 1 28 Freescale Semiconductor MSC8113 Overview ...
Page 76: ...MSC8113 Reference Manual Rev 0 2 20 Freescale Semiconductor SC140 Core Overview ...
Page 134: ...MSC8113 Reference Manual Rev 0 4 30 Freescale Semiconductor System Interface Unit SIU ...
Page 168: ...MSC8113 Reference Manual Rev 0 6 18 Freescale Semiconductor Boot Program ...
Page 180: ...MSC8113 Reference Manual Rev 0 7 12 Freescale Semiconductor Clocks ...
Page 260: ...MSC8113 Reference Manual Rev 0 8 80 Freescale Semiconductor Memory Map ...
Page 300: ...MSC8113 Reference Manual Rev 0 9 40 Freescale Semiconductor Extended Core ...
Page 304: ...MSC8113 Reference Manual Rev 0 10 4 Freescale Semiconductor MQBus and M2 Memory ...
Page 308: ...MSC8113 Reference Manual Rev 0 11 4 Freescale Semiconductor SQBus ...
Page 590: ...MSC8113 Reference Manual Rev 0 17 46 Freescale Semiconductor Interrupt Processing ...
Page 614: ...MSC8113 Reference Manual Rev 0 18 24 Freescale Semiconductor Debugging ...
Page 622: ...MSC8113 Reference Manual Rev 0 19 8 Freescale Semiconductor Internal Peripheral Bus IPBus ...
Page 724: ...MSC8113 Reference Manual Rev 0 21 32 Freescale Semiconductor UART ...
Page 920: ...MSC8113 Reference Manual Rev 0 25 150 Freescale Semiconductor Ethernet Controller ...
Page 1171: ...MSC8113 Reference Manual Rev 0 Freescale Semiconductor C 61 EF wait_rts P 01077FFC 9F rts 71 ...
Page 1172: ...MSC8113 Reference Manual Rev 0 C 62 Freescale Semiconductor MSC8113 Boot Code ...
Page 1202: ...MSC8113 Reference Manual Rev 0 Index 30 Freescale Semiconductor Index ...