Motorola MPC8260 - Manual (Page 696)

25-4 MPC8260 PowerQUICC II UserÕs Manual MOTOROLA
Part IV. Communications Processor Module
5. Clear TEND for default operation.
6. Set TPP to 0b11 for a preamble pattern of all ones.
7. Set TPL to 0b000 to transmit the next frame with no synchronization sequence and
to 001 to transmit the next frame with the LocalTalk synchronization sequence. For
example, data frames do not require a preceding synchronization sequence. These
bits may be modiÞed on-the-ßy if the AppleTalk protocol is selected.
8. Clear TINV and RINV so data will not be inverted.
9. Set TSNC to 1.5 bit times (0b10).
10. Clear EDGE. Both the positive and negative edges are used to change the sample
point (default).
11. Clear RTSM (default).
12. Set all other bits to zero or default.
13. Set ENT and ENR as the last step to begin operation.
25.4.2 Programming the PSMR
Follow these steps to program the protocol-speciÞc mode register:
1. Set NOF to 0b0001 giving two ßags before frames (one opening ßag, plus one
additional ßag).
2. Set CRC 16-bit CRC-CCITT.
3. Set DRT.
4. Set all other bits to zero or default.
For the PSMR deÞnition, see Section 21.8, ÒHDLC Mode Register (PSMR).Ó
25.4.3 Programming the TODR
Use the transmit-on-demand (TODR) register to expedite a transmit frame. See
Section 19.1.4, ÒTransmit-on-Demand Register (TODR).Ó
25.4.4 SCC AppleTalk Programming Example
Except for the previously discussed register programming, use the example in
Section 21.14.6, ÒHDLC Bus Protocol Programming.У