MC68HC705C9A_1 Datasheet, PDF (83/157 Pages) Freescale Semiconductor, Inc – General Release Specification

Freescale Semiconductor, Inc.
General Release Specification
Functional Description
interrupts are enabled). The transfer of data to the transmit data shift
register is synchronized with the bit rate clock (see Figure 9-2). All data
is transmitted least significant bit first. Upon completion of data
transmission, the transmission complete flag (TC) in the SCSR is set
(provided no pending data, preamble, or break is to be sent) and an
interrupt is generated (if the transmit complete interrupt is enabled). If
the transmitter is disabled, and the data, preamble, or break (in the
transmit data shift register) has been sent, the TC bit will be set also.
This will also generate an interrupt if the transmission complete interrupt
enable bit (TCIE) is set. If the transmitter is disabled during a
transmission, the character being transmitted will be completed before
the transmitter gives up control of the TDO pin.
When SCDR is read, it contains the last data byte received, provided
that the receiver is enabled. The receive data register full flag bit (RDRF)
in the SCSR is set to indicate that a data byte has been transferred from
the input serial shift register to the SCDR; this will cause an interrupt if
the receiver interrupt is enabled. The data transfer from the input serial
shift register to the SCDR is synchronized by the receiver bit rate clock.
The OR (overrun), NF (noise), or FE (framing) error flags in the SCSR
may be set if data reception errors occurred.
An idle line interrupt is generated if the idle line interrupt is enabled and
the IDLE bit (which detects idle line transmission) in SCSR is set. This
allows a receiver that is not in the wakeup mode to detect the end of a
message, or the preamble of a new message, or to re-synchronize with
the transmitter. A valid character must be received before the idle line
condition or the IDLE bit will not be set and idle line interrupt will not be
generated.
OSC FREQ
(f_OSC)
÷2
BUS FREQ
(f_OP)
SCP0–SCP1
SCI PRESCALER
SELECT
CONTROL
N
SCR0–SCR2
SCI RATE
SELECT
CONTROL
M
SCI RECEIVE
CLOCK (RT)
Figure 9-2. Rate Generator Division
SCI TRANS
÷16
CLOCK (TX)
MC68HC705C9A — Rev. 2.0
Serial Communications Interface (SCI)
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