Motorola MPC8260 User Manual

MOTOROLA

Chapter 21. SCC HDLC Mode

21-23

Part IV. Communications Processor Module

21.14.6 HDLC Bus Protocol Programming

The HDLC bus on the MPC8260 is implemented using the SCC in HDLC mode with bus-
speciÞc options selected in the PSMR and GSMR, as outlined below. See also Section 21.5,
ÒProgramming the SCC in HDLC Mode.Ó

21.14.6.1 Programming GSMR and PSMR for the HDLC Bus Protocol

To program the protocol-speciÞc mode register (PSMR), set the bits as described below:

ConÞgure NOF as preferred

Set RTE and BUS to 1

Set BRM to 1 if delayed RTS is desired

ConÞgure CRC to 16-bit CRC CCITT (0b00).

ConÞgure other bits to zero or default.

To program the general SCC mode register (GSMR), set the bits as described below:

Set MODE to HDLC mode (0b0000).

ConÞgure CTSS to 1 and all other bits to zero or default.

ConÞgure the DIAG bits for normal operation (0b00).

ConÞgure RDCR and TDCR for 1

´ clock (0b00).

ConÞgure TENC and RENC for NRZ (0b000).

Clear RTSM to send idles between frames.

Set GSMR_L[ENT, ENR] as the last step to begin operation.

21.14.6.2 HDLC Bus Controller Programming Example