MC68HC708AS48 FREESCALE [Freescale Semiconductor, Inc], MC68HC708AS48 Datasheet - Page 260

• Manufacturer Part Number: MC68HC708AS48
• Description: Advance Information
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Serial Communications Interface (SCI)
17.4.13 Framing Errors
17.4.14 Receiver Wakeup
Advance Information
260
NOTE:
The RT8, RT9, and RT10 samples do not affect start bit verification. If
any or all of the RT8, RT9, and RT10 start bit samples are logic 1s
following a successful start bit verification, the noise flag (NF) is set and
the receiver assumes that the bit is a start bit.
To verify a stop bit and to detect noise, recovery logic takes samples at
RT8, RT9, and RT10.
samples.
If the data recovery logic does not detect a logic 1 where the stop bit
should be in an incoming character, it sets the framing error bit, FE, in
SCS1. The FE flag is set at the same time that the SCRF bit (SCS1) is
set. A break character that has no stop bit also sets the FE bit.
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 (SCC2), puts the
receiver into a standby state during which receiver interrupts are
disabled.
Serial Communications Interface (SCI)
RT8, RT9, and RT10
Table 17-3. Stop Bit Recovery
Samples
Table 17-3
000
001
010
011
100
101
110
111
summarizes the results of the stop bit
Error Flag
Framing
1
1
1
0
1
0
0
0
MC68HC708AS48
Noise Flag
0
1
1
1
1
1
1
0
MOTOROLA
—
Rev. 4.0