MPC823 datasheet(36/74 Pages) MOTOROLA

36 / 74 page

Communication Processor Module

16-414

MPC823 REFERENCE MANUAL

MOTOROLA

CLEN—Character Length

This field is programmed with a value between 3 and 15 to obtain 4 to 16 bits per character.

If the character length is less than 8 bits, the MSBs of the byte in buffer memory are not used

on transmit and are written with zeros on receive. On the other hand, if the character length

is more than 8 bits but less than 16 bits, the MSBs of the half-word in buffer memory are not

used on transmit and are written with zeros on receive.

BS—Byte Sequence

This bit controls the sequence of byte transmission if the REVD bit is set for a character

length greater than 8 bits. It must be set to zero to maintain behavior compatibility with the

MC68360 QUICC microprocessor.

0 = Normal mode. This must be selected if the character length is less than

or equal to 8 bits.

1 = Transmit lower address byte first.

REVD—Reverse Data

0 = Normal mode.

1 = Reverse the character bit order. The MSB is transmitted first.

SM—SMCx Mode

00 = GCI or SCIT mode.

01 = Reserved.

10 = UART mode.

11 = Totally transparent mode. This must be selected for SMCx transparent operation.

DM—Diagnostic Mode

00 = Normal mode.

01 = Local loopback mode.

10 = Echo mode.

11 = Reserved.

TEN—SMCx Transmit Enable

0 = SMCx transmitter disabled.

1 = SMCx transmitter enabled.

Note: Erratic behavior will occur if you do not write the values 0 to 2 to CLEN. Larger

character lengths increase the potential performance of the SMCx channel and

lower the performance impact of other channels. For instance, using 16-bit

characters, rather than 8-bit characters is recommended if 16-bit characters are

acceptable in the final application.

Note: Once the TEN bit is cleared, it must not be reenabled for at least

three serial clocks.

MPC823 Datasheet(PDF) 36 Page - Motorola, Inc