MMC2107 - Freescale Semiconductor

Freescale Semiconductor, Inc.
Serial Communications Interface Modules (SCI1 and SCI2)
Transmitter
16.11.2 Transmitting a Frame
To begin an SCI transmission:
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Freescale Semiconductor, I
1. Configure the SCI:
a. Write a baud rate value to SCIBDH and SCIBDL.
b. Write to SCICR1 to:
i. Enable or disable loop mode and select the receiver
feedback path
ii.
iii.
iv.
Select open-drain or wired-OR SCI outputs
Select 10-bit or 11-bit frames
Select the receiver wakeup condition: address mark or
idle line
v. Select idle line type
vi.
Enable or disable the parity function and select odd or
even parity
c. Write to SCICR2 to:
i. Enable or disable TDRE, TC, RDRF, and IDLE interrupt
requests
ii.
iii.
iv.
2. Transmit a byte:
Enable the transmitter and queue a break frame
Enable or disable the receiver
Put the receiver in standby if required
a. Clear the TDRE flag by reading SCISR1 and, if sending 9-bit
data, write the ninth data bit to SCDRH.
b. Write the byte to be transmitted (or low-order 8 bits if sending
9-bit data) to SCIDRL.
3. Repeat step 2 for each subsequent transmission.
Writing the TE bit from 0 to 1 loads the transmit shift register with a
preamble of 10 (if M = 0) or 11 (if M = 1) logic 1s. When the preamble
shifts out, the SCI transfers the data from SCIDRH and SCIDRL to the
transmit shift register. The transmit shift register prefaces the data with
a 0 start bit and appends the data with a 1 stop bit and begins shifting
out the frame.
MMC2107 – Rev. 2.0
Technical Data
MOTOROLA Serial Communications Interface Modules (SCI1 and SCI2) 353
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