Freescale Semiconductor MPC8260 - Manual (Page 1229)

FCC HDLC Controller
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 36-5
Figure 36-2. HDLC Address Recognition Example
36.5 Programming Model
The core configures each FCC to operate in the protocol specified in GFMR[MODE]. The HDLC
controller uses the same data structure as other modes. This data structure supports multibuffer operation
and address comparisons.
36.5.1 HDLC Command Set
The transmit and receive commands are issued to the CPCR; see Section 14.4, “Command Set.”
Table 36-2 describes the transmit commands that apply to the HDLC controller.
Table 36-2. Transmit Commands
Command Description
STOP TRANSMIT After the hardware or software is reset and the channel is enabled in the FCC mode register, the
channel is in transmit enable mode and starts polling the first BD in the table every 256 transmit
clocks (immediately if FTODR[TOD] = 1).
STOP TRANSMIT command disables the transmission of
frames on the transmit channel. If this command is received by the HDLC controller during frame
transmission, transmission is aborted after a maximum of 64 additional bits are sent and the transmit
FIFO buffer is flushed. The TBPTR is not advanced, no new BD is accessed, and no new frames
are sent for this channel. The transmitter sends an abort sequence consisting of 0x7F (if the
command was given during frame transmission) and begins sending flags or idles, as indicated by
the HDLC mode register. Note that if FPSMR[MFF] = 1, one or more small frames can be flushed
from the transmit FIFO buffer. The
GRACEFUL STOP TRANSMIT command can be used to avoid this.
GRACEFUL STOP
TRANSMIT
Used to stop transmission smoothly rather than abruptly, as performed by the regular STOP TRANSMIT
command. It stops transmission after the current frame finishes sending or immediately if no frame
is being sent. FCCE[GRA] is set once transmission has stopped. Then the HDLC transmit
parameters (including BDs) can be modified. The TBPTR points to the next TxBD in the table.
Transmission begins once the R bit of the next BD is set and the
RESTART TRANSMIT command is
issued.
HMASK
8-Bit Address Recognition
Address
0x68
Control
0x44
Flag
0x7E
Address
0xAA
etc.
16-Bit Address Recognition
0xFFFF
0xAA68
0xFFFF
0xAA68
0xAA68
HMASK
Address
0x55
Control
0x44
Flag
0x7E
etc.
0x00FF
0xXX55
0xXX55
0xXX55
0xXX55
HADDR1
HADDR2
HADDR3
HADDR4
HADDR1
HADDR2
HADDR3
HADDR4
Recognizes one 16-bit address (HADDR1) and
the 16-bit broadcast address (HADDR2) Recognizes one 8-bit address (HADDR1)