MC68HC908GR4MP datasheet(248/408 Pages) FREESCALE

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Serial Communications Interface (SCI)

Technical Data

MC68HC908GR8 — Rev 4.0

248

Serial Communications Interface (SCI)

MOTOROLA

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 18-8, 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

18.5.3.8 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:

•

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

receiver. If they are the same, the receiver remains awake and

processes the characters that follow. If they are not the same,

software can set the RWU bit and put the receiver back into the

standby state.

•

Idle input line condition — When the WAKE bit is clear, an idle

character on the PE1/RxD pin wakes the receiver from the

standby state by clearing the RWU bit. The idle character that

wakes the receiver does not set the receiver idle bit, IDLE, or the

170

176

–

170

--------------------------

100

3.53%

Freescale Semiconductor, Inc.

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