MPC5553/MPC5554 Microcontroller Reference Manual, Rev. 5
Freescale Semiconductor 21-29
For an 8-bit data character, data sampling of the stop bit takes the receiver RT clock 151 clock cycles, as
is shown below:
With the misaligned character shown in Figure 21-19, the receiver counts 151 RT cycles at the point when
the count of the transmitting device is 9 bit times x 16 RT cycles = 147 RT cycles.
The maximum percent difference between the receiver count and the transmitter count of a slow 8-bit data
character with no errors is 4.63%, as is shown below:
For a 9-bit data character, data sampling of the stop bit takes the receiver 167 RT cycles, as is shown below:
With the misaligned character shown in Figure 21-19, the receiver counts 167 RT cycles at the point when
the count of the transmitting device is 10 bit times x 16 RT cycles = 160 RT cycles.
The maximum percent difference between the receiver count and the transmitter count of a slow 9-bit
character with no errors is 4.19%, as is shown below:
21.4.5.5.2 Fast Data Tolerance
Figure 21-20 shows how much a fast received frame can be misaligned. The fast stop bit ends at RT10
instead of RT16 but is still sampled at RT8, RT9, and RT10.
Figure 21-20. Fast Data
For an 8-bit data character, data sampling of the stop bit takes the receiver 154 RT cycles, as is shown
below:
With the misaligned character shown in Figure 21-20, the receiver counts 154 RT cycles at the point when
the count of the transmitting device is 10 bit times x 16 RT cycles = 160 RT cycles.
The maximum percent difference between the receiver count and the transmitter count of a fast 8-bit
character with no errors is 3.40%, as is shown below:
9 bit times 16 RT cycles 7 RT cycles+ 151 RT cycles=
151 – 144
151
--------------------------
100 4.63%=
10 bit times 16 RT cycles 7 RT cycles+ 167 RT cycles =
167 – 160
167
--------------------------
100 4.19%=
RT1
Receiver
RT Clock
RT2 RT3 RT4 RT5 RT6 RT7 RT8 RT9 RT10 RT11 RT12 RT13 RT14 RT15 RT16
STOP IDLE or Next Frame
Data Samples
9 bit times 16 RT cycles 10 RT cycles+ 154 RT cycles=
160 – 154
160
--------------------------
100 3.40%=
To Next Page
Loading...