Fast Communications Controllers (FCCs)
MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 29-5
3 TRX Transparent receiver. The PowerQUICCII FCCs offer totally transparent operation. However, to
increase flexibility, totally transparent operation is configured with the TTX and TRX bits instead of
the MODE bits. This lets the user implement unique applications such as an FCC transmitter
configured to HDLC and a receiver configured to totally transparent operation. To do this, program
MODE = HDLC, TTX = 0, and TRX = 1.
0 Normal operation
1 The receiver operates in totally transparent mode, regardless of the protocol selected for the
transmitter in the MODE bits.
Note:Full-duplex, totally transparent operation for an FCC is obtained by setting both TTX and TRX.
Attempting to operate an FCC with Ethernet or ATM on its transmitter and transparent
operation on its receiver causes erratic behavior. In other words, if the MODE = Ethernet or
ATM, TTX must equal TRX.
4 TTX Transparent transmitter. The PowerQUICCII FCCs offer totally transparent operation. However, to
increase flexibility, totally transparent operation is configured with the TTX and TRX bits instead of
the MODE bits. This lets the user implement unique applications, such as configuring an FCC
receiver to HDLC and a transmitter to totally transparent operation. To do this, program MODE =
HDLC, TTX = 1, and TRX = 0.
0 Normal operation.
1 The transmitter operates in totally transparent mode, regardless of the receiver protocol selected
in the MODE bits.
Note:Full-duplex totally transparent operation for an FCC is obtained by setting both TTX and TRX.
Attempting to operate an FCC with Ethernet or ATM on its receiver and transparent operation
on its transmitter causes erratic behavior. In other words, if GFMR[MODE] selects Ethernet
or ATM, TTX must equal TRX.
5 CDP CD pulse (transparent mode only)
0 Normal operation (envelope mode). CD should envelope the frame; to negate CD while receiving
causes a CD lost error.
1 Pulse mode. Once CD is asserted (high to low transition), synchronization has been achieved,
and further transitions of CD do not affect reception.
Note:CDP must be set if this FCC is used with the TSA in transparent mode.
6 CTSP CTS pulse
0 Normal operation (envelope mode). CTS should envelope the frame; to negate CTS while
transmitting causes a CTS lost error. See Section29. 11, “FCC Timing Control.”
1 Pulse mode. CTS is asserted when synchronization is achieved; further transitions of CTS do not
affect transmission. When running HDLC, the FCC samples CTS only once before sending the
first frame after the transmitter is enabled (ENT = 1).
7 CDS CD sampling
0 The CD input is assumed to be asynchronous with the data. The FCC synchronizes it internally
before data is received. (This mode is not allowed in transparent mode when SYNL = 0b00.)
1 The CD input is assumed to be synchronous with the data, giving faster operation. In this mode,
CD must transition while the receive clock is in the low state. When CD goes low, data is received.
This is useful when connecting PowerQUICCIIs in transparent mode since it allows the RTS
signal of one PowerQUICCII to be connected directly to the CD signal of another PowerQUICCII.
Table29-2. GFMR Register Field Descriptions (continued)
Bits Name Description