Motorola MPC8260 User Manual

Page 764

28-6

MPC8260 PowerQUICC II UserÕs Manual

MOTOROLA

Part IV. Communications Processor Module

22Ð23 TENC

Transmitter encoding method. The user should set TENC = RENC in most applications.
00 NRZ
01 NRZI (one bit mode HDLC or transparent only)
1x Reserved

24-25 TCRC

Transparent CRC (totally transparent channel only). Selects the type of frame checking provided on
the transparent channels of the FCC (either the receiver, transmitter, or both, as deÞned by TTX
and TRX). This conÞguration selects a frame check type; the decision to send the frame check is
made in the TxBD. Thus, it is not required to send a frame check in transparent mode. If a frame
check is not used, the user can ignore any frame check errors generated on the receiver.
00 16-bit CCITT CRC (HDLC). (X16 + X12 + X5 + 1)
01 Reserved
10 32-bit CCITT CRC (Ethernet and HDLC) (X32 + X26 + X23 + X22 + X16 + X12 + X11 + X10 +

X8 + X7 + X5 + X4 + X2 + X1 +1)

11 Reserved

ENR

Enable receive. Enables the receiver hardware state machine for this FCC.
0 The receiver is disabled and any data in the receive FIFO buffer is lost. If ENR is cleared during

reception, the receiver aborts the current character.

1 The receiver is enabled.
ENR may be set or cleared regardless of whether serial clocks are present. Describes how to
disable and reenable an FCC. Note that the FCC provides other tools for controlling receptionÑthe

ENTER

HUNT

MODE

command,

RXBD

command, and RxBD[E].

ENT

Enable transmit. Enables the transmitter hardware state machine for this FCC.
0 The transmitter is disabled. If ENT is cleared during transmission, the transmitter aborts the

current character and TXD returns to idle state. Data in the transmit shift register is not sent.

1 The transmitter is enabled.
ENT can be set or cleared, regardless of whether serial clocks are present. See Section 28.12,
ÒDisabling the FCCs On-the-Fly,Ó for a description of the proper methods to disable and reenable an
FCC. Note that the FCC provides other tools for controlling transmission besides the ENT bitÑthe

STOP

TRANSMIT

GRACEFUL

STOP

TRANSMIT

, and

RESTART

TRANSMIT

commands, CTS ßow control,

and TxBD[R].

28Ð31 MODE

Channel protocol mode
0000 HDLC
0001 Reserved for RAM microcode
0010 Reserved
0011 Reserved for RAM microcode
0100 Reserved
0101 Reserved for RAM microcode
0110 Reserved
0111 Reserved for RAM microcode
1000 Reserved
1001 Reserved for RAM microcode
1010 ATM
1011 Reserved for RAM microcode
1100 Ethernet
11xx Reserved

Table 28-1. GFMR Register Field Descriptions (Continued)

Field

Name Description