Freescale Semiconductor MPC8260 Benutzerhandbuch
Fast Communications Controllers (FCCs)
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
29-4
Freescale Semiconductor
Table 29-2. describes GFMR fields.
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
Field
DIAG
TCI
TRX
TTX
CDP
CTSP CDS CTSS
—
Reset
0000_0000_0000_0000
R/W
R/W
Addr
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
Field
SYNL
RTSM
RENC
REVD
TENC
TCRC
ENR ENT
MODE
Reset
0000_0000_0000_0000
R/W
R/W
Addr
0x11302 (GFMR1), 0x11322 (GFMR2), 0x11342 (GFMR3)
Figure 29-2. General FCC Mode Register (GFMR)
Table 29-2. GFMR Register Field Descriptions
Bits
Name Description
0–1
DIAG
Diagnostic mode.
00 Normal operation—Receive data enters through RXD, and transmit data is shifted out through
00 Normal operation—Receive data enters through RXD, and transmit data is shifted out through
TXD. The FCC uses the modem signals (CD and CTS) to automatically enable and disable
transmission and reception. Timings are shown in
transmission and reception. Timings are shown in
01 Local loopback mode—Transmitter output is connected internally to the receiver input, while the
receiver and the transmitter operate normally. RXD is ignored. Data can be programmed to
appear on TXD, or TXD can remain high by programming the appropriate parallel port register.
RTS can be disabled in the appropriate parallel I/O register. The transmitter and receiver must
use the same clock source, but separate CLK
appear on TXD, or TXD can remain high by programming the appropriate parallel port register.
RTS can be disabled in the appropriate parallel I/O register. The transmitter and receiver must
use the same clock source, but separate CLK
x pins can be used if connected to the same
external clock source.
If external loopback is preferred, program DIAG for normal operation and externally connect TXD
and RXD. Then, physically connect the control signals (RTS connected to CD, and CTS
grounded) or set the parallel I/O registers so CD and CTS are permanently asserted to the FCC
by configuring the associated CTS and CD pins as general-purpose I/O.; see
If external loopback is preferred, program DIAG for normal operation and externally connect TXD
and RXD. Then, physically connect the control signals (RTS connected to CD, and CTS
grounded) or set the parallel I/O registers so CD and CTS are permanently asserted to the FCC
by configuring the associated CTS and CD pins as general-purpose I/O.; see
.”
10 Automatic echo mode—The channel automatically retransmits received data, using the receive
clock provided. The receiver operates normally and receives data if CD is asserted. The
transmitter simply transmits received data. In this mode, CTS is ignored. The echo function can
also be accomplished in software by receiving buffers from an FCC, linking them to TxBDs, and
transmitting them back out of that FCC.
transmitter simply transmits received data. In this mode, CTS is ignored. The echo function can
also be accomplished in software by receiving buffers from an FCC, linking them to TxBDs, and
transmitting them back out of that FCC.
11 Loopback and echo mode—Loopback and echo operation occur simultaneously. CD and CTS
are ignored. Refer to the loopback bit description for clocking requirements.
For TDM operation, the diagnostic mode is selected by SI
xMR[SDMx]; see
2
TCI
Transmit clock invert
0
0
Normal operation.
1
The FCC inverts the internal transmit clock.
The edge on which the FCC outputs the data depends on the protocol:
• In HDLC and Transparent mode, when TCI=0, data is sent on the falling edge; when TCI=1, on
• In HDLC and Transparent mode, when TCI=0, data is sent on the falling edge; when TCI=1, on
the rising edge.
• In Ethernet mode, when TCI=0, data is sent on the rising edge; when TCI=1, on the falling edge.