Chapter 13 Serial Communications Interface (S12SCIV2) Block Description
Freescale Semiconductor
MC9S12C-Family / MC9S12GC-Family
407
Rev 01.24
With the misaligned character shown in
, the receiver counts 167 RTr cycles at the point when
the count of the transmitting device is 10 bit times x 16 RTt cycles = 160 RTt cycles.
The maximum percent difference between the receiver count and the transmitter count of a slow 9-bit
character with no errors is:
((167 – 160) / 167) X 100 = 4.19%
13.4.4.5.2
Fast Data Tolerance
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 13-21. Fast Data
For an 8-bit data character, it takes the receiver 9 bit times x 16 RTr 10 RTr cycles = 154 RTr cycles
to finish data sampling of the stop bit.
With the misaligned character shown in
, the receiver counts 154 RTr cycles at the point when
the count of the transmitting device is 10 bit times x 16 RTt cycles = 160 RTt cycles.
The maximum percent difference between the receiver count and the transmitter count of a fast 8-bit
character with no errors is:
((160 – 154) / 160) x 100 = 3.75%
For a 9-bit data character, it takes the receiver 10 bit times x 16 RTr 10 RTr cycles = 170 RTr cycles
to finish data sampling of the stop bit.
With the misaligned character shown in
, the receiver counts 170 RTr cycles at the point when
the count of the transmitting device is 11 bit times x 16 RTt cycles = 176 RTt cycles.
The maximum percent difference between the receiver count and the transmitter count of a fast 9-bit
character with no errors is:
((176 – 170) / 176) x 100 = 3.40%
13.4.4.6
Receiver Wakeup
To enable the SCI to ignore transmissions intended only for other receivers in multiple-receiver systems,
the receiver can be put into a standby state. Setting the receiver wakeup bit, RWU, in SCI control register
2 (SCICR2) puts the receiver into standby state during which receiver interrupts are disabled.The SCI will
still load the receive data into the SCIDRH/L registers, but it will not set the RDRF flag.
IDLE OR NEXT FRAME
STOP
RT1
RT2
RT3
RT4
RT5
RT6
RT7
RT8
RT9
RT10
RT11
RT12
RT13
RT14
RT15
RT16
DATA
SAMPLES
RECEIVER
RT CLOCK
Summary of Contents for MC9S12C Family
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