
Serial Communications Interface Module (SCI)
Functional Description
MC68HC(9)08LJ60 — Rev. 1.0
Advance Information
MOTOROLA
Serial Communications Interface Module (SCI)
191
NON-DISCLOSURE
AGREEMENT
REQUIRED
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 Figure 12-8, 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
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 12-8, 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
12.4.3.6 Receiver Wakeup
So that the MCU can ignore transmissions intended only for other
receivers in multiple-receiver systems, the MCU can be put into a
standby state. Setting the receiver wakeup bit, RWU, in SCC2 puts the
MCU 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 RxD pin can bring the MCU out of the standby state:
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 flag, SCRF. Software can then compare the character
containing the address mark to the user-defined address of the
154
160
–
154
--------------------------
100
×
3.90%
˙
=
170
176
–
170
--------------------------
100
×
3.53%
=
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Freescale Semiconductor, Inc.
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