MC68HC05X16 Datasheet, PDF (109/232 Pages) Freescale Semiconductor, Inc – High-density complementary metal oxide semiconductor HCMOS) microcontroller unit

Freescale Semiconductor, Inc.
16X internal sampling clock
RT clock edges for all three examples
1RT 2RT 3RT 4RT 5RT 6RT 7RT 8RT
Idle
Start
RDI
111111111110
Start
qualifiers
0
0
0
Start edge
verification samples
Start
RDI
111111111110
Noise
0
1
0
Noise
Start
RDI
111110111110
0
0
0
Figure 7-4 SCI examples of start bit sampling technique
7
Previous bit
Present bit
RDI
16RT 1RT
Samples
8RT 9RT 10RT
Next bit
16RT 1RT
Figure 7-5 SCI sampling technique used on all bits
edge will be placed artificially. The last bit received in the data shift register is inverted to a logic
one, and the three logic one start qualifiers (shown in Figure 7-4) are forced into the sample shift
register during the interval when detection of a start bit is anticipated (see Figure 7-6); therefore,
the start bit will be accepted no sooner than it is anticipated.
MC68HC05X16
SERIAL COMMUNICATIONS INTERFACE
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