MCCIRM Freescale Semiconductor / Motorola, MCCIRM Datasheet - Page 61

• Manufacturer Part Number: MCCIRM
• Description: MCCIRM Multi-Channel Communications Interface Reference Manual
• Manufacturer: Freescale Semiconductor / Motorola

Multichannel Communication Interface — Rev. 1.0
MOTOROLA
The SCI transmitter automatically provides a start bit as the first bit of
each frame and a stop bit as the final bit. In addition, it generates a parity
bit preceding the stop bit, if parity is enabled. The SCI receiver
automatically strips the start and stop bits. If parity is enabled, the
receiver strips the parity bit as well. Receiving and transmitting devices
must use the same data frame format.
The SCI provides hardware support for both 10- and 11-bit frames. The
most common 10-bit data frame format for NRZ serial interface is one
start bit, eight data bits (LSB first), and one stop bit. The most common
11-bit data frame contains one start bit, eight data bits, a parity or
address mark bit, and one stop bit.
The serial mode bit in SCCR1 specifies the number of bits per frame.
The PE bit determines whether the MSB is a parity bit. (For transmitted
data, a parity bit is generated; for received data, the parity bit is
checked.) When parity is disabled, software can use the MSB as an
address mark bit or a second stop bit. When parity is enabled, the
address mark or second stop bit options are not available.
Table 5-3
provides four frame formats, according to the values of M and PE. Within
these four formats, software can provide additional variations.
M
0
0
1
1
•
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PE
MSB — Most significant bit; in a data frame, the bit preceding the
hardware-generated stop bit. Depending on the hardware and
software configuration, the MSB (most significant bit) may
represent a data bit, parity bit, address mark bit, or extra stop bit.
0
1
0
1
lists the possible frame formats. Notice that hardware
1 start bit, 8 data bits, 1 stop bit
1 start bit, 7 data bits, 1 address mark bit, 1 stop bit
1 start bit, 7 data bits, 2 stop bits
1 start bit, 7 data bits, 1 parity bit, 1 stop bit
1 start bit, 8 data bits, 1 address mark bit, 1 stop bit
1 start bit, 8 data bits, 2 stop bits
1 start bit, 8 data bits, 1 parity bit, 1 stop bit
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SCI Submodule
Table 5-3. Data Frame Formats
Frame Format
Reference Manual
SCI Submodule
Serial Formats
61