MC9S12T64 Datasheet, PDF (451/608 Pages) Motorola, Inc – Specification

Freescale Semiconductor, Inc.
Serial Communications Interface (SCI)
Functional Description
With the misaligned character shown in Figure 88, the receiver counts
154 RT cycles at the point when the count of the transmitting device is
10 bit times x 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:
((154 – 160) / 154) x 100 = 3.90%
For a 9-bit data character, data sampling of the stop bit takes the
receiver 10 bit times x 16 RT cycles + 10 RT cycles = 170 RT cycles.
With the misaligned character shown in Figure 88, the receiver counts
170 RT cycles at the point when the count of the transmitting device is
11 bit times x 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:
((170 – 176) / 170) x 100 = 3.53%
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 (SCIxCR2) puts the receiver into a standby state during which
receiver interrupts are disabled.The SCI will still load the receive data
into the SCIxDRH/L registers, but it will not set the RDRF flag.
The transmitting device can address messages to selected receivers by
including addressing information in the initial frame or frames of each
message.
The WAKE bit in SCI control register 1 (SCIxCR1) determines how the
SCI is brought out of the standby state to process an incoming message.
The WAKE bit enables either idle line wakeup or address mark wakeup.
Idle input line
wakeup
(WAKE = 0)
In this wakeup method, an idle condition on the RX input signal clears
the RWU bit and wakes up the SCI. The initial frame or frames of every
message contain addressing information. All receivers evaluate the
addressing information, and receivers for which the message is
Serial Communications Interface (SCI)
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MC9S12T64Revision 1.1.1