mc68hc908gr8vp Freescale Semiconductor, Inc, mc68hc908gr8vp Datasheet - Page 172

• Manufacturer Part Number: mc68hc908gr8vp
• Description: M68hc08 Microcontrollers Microcontroller
• Manufacturer: Freescale Semiconductor, Inc

Serial Communications Interface (SCI)
18.4.3.7 Fast Data Tolerance
Figure 18-8
or a framing error. The fast stop bit ends at RT10 instead of RT16 but is still there for the stop bit data
samples at RT8, RT9, and RT10.
For an 8-bit character, data sampling of the stop bit takes the receiver
9 bit times × 16 RT cycles + 10 RT cycles = 154 RT cycles.
With the misaligned character shown in
the count of the transmitting device is 10 bit times × 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
For a 9-bit character, data sampling of the stop bit takes the receiver
10 bit times × 16 RT cycles + 10 RT cycles = 170 RT cycles.
With the misaligned character shown in
the count of the transmitting device is 11 bit times × 16 RT cycles = 176 RT cycles.
The maximum percent difference between the receiver count and the transmitter count of a fast 9-bit
character with no errors is
18.4.3.8 Receiver Wakeup
So that the MCU can 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 SCC2 puts the
receiver into a standby state during which receiver interrupts are disabled.
Depending on the state of the WAKE bit in SCC1, either of two conditions on the PE1/RxD pin can bring
the receiver out of the standby state:
172
•
Address mark — An address mark is a logic 1 in the most significant bit position of a received
character. When the WAKE bit is set, an address mark wakes the receiver from the standby state
by clearing the RWU bit. The address mark also sets the SCI receiver full bit, SCRF. Software can
then compare the character containing the address mark to the user-defined address of the
shows how much a fast received character can be misaligned without causing a noise error
RECEIVER
RT CLOCK
MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7
170 176
------------------------- -
154 160
------------------------- -
Figure
Figure
STOP
Figure 18-8. Fast Data
170
154
–
–
18-8, the receiver counts 154 RT cycles at the point when
18-8, the receiver counts 170 RT cycles at the point when
×
×
100
100
SAMPLES
DATA
=
=
3.53%
3.90%
·
IDLE OR NEXT CHARACTER
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