MC68908GZ8MFJE Datasheet, PDF (193/314 Pages) Freescale Semiconductor, Inc – Microcontrollers

Functional Description
The maximum percent difference between the receiver count and the transmitter count of a slow 9-bit
character with no errors is:
-1---7---0-----^–----1----6---3-- ^{× 100 = 4.12%}
170
Fast Data Tolerance
Figure 15-9 shows how much a fast received character can be misaligned without causing a noise error
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.
STOP
IDLE OR NEXT CHARACTER
RECEIVER
RT CLOCK
DATA
SAMPLES
Figure 15-9. Fast Data
For an 8-bit character, data sampling of the stop bit takes the receiver9 bit times × 16 RT cycles +
10 RT cycles = 154 RT cycles.
With the misaligned character shown in Figure 15-9, the receiver counts 154 RT cycles at the point when
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
-1---5---4-----^–----1----6---0-- ^{× 100 = 3.90%.}
154
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 Figure 15-9, the receiver counts 170 RT cycles at the point when
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:
-1---7---0-----^–----1----7---6-- ^{× 100 = 3.53%.}
170
15.4.3.6 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.
MC68HC908GZ16 • MC68HC908GZ8 Data Sheet, Rev. 4
Freescale Semiconductor
193