Serial Communication Controllers (SCCs)
MOTOROLA
MC68360 USER’S MANUAL
7-115
receiver begins receiving data. This behavior is similar to the MC68302 totally
transparent mode behavior when the EXSYN bit in its SCC mode register is set.
SYNL—Sync Length (BISYNC and Transparent Mode Only)
These bits determine the operation of an SCC receiver that is configured for BISYNC or
totally transparent operation only. See the data synchronization register definition in the
BISYNC and totally transparent descriptions for more information.
00 = The sync pattern in the DSR is not used. An external sync signal is used instead
(CD pin asserted).
01 = 4-bit sync. The receiver will synchronize on a 4-bit sync pattern stored in DSR.
This character and additional syncs can be programmed to be stripped using the
SYNC character in the parameter RAM. The transmitter will transmit the entire
contents of the DSR prior to each frame.
10 = 8-bit sync. This option should be chosen along with the BISYNC protocol to im-
plement mono-sync. The receiver will synchronize on an 8-bit sync pattern stored
in DSR. The transmitter will transmit the entire contents of the DSR prior to each
frame.
11 = 16-bit sync. Also called BISYNC. The receiver will synchronize on a 16-bit sync
pattern stored in DSR. The transmitter will transmit the DSR prior to each frame.
RTSM—RTS Mode
This bit may be changed on the fly.
0 = Send idles between frames as defined by the protocol and the Tend bit. RTS is ne-
gated between frames (default).
1 = Send flags/syncs between frames according to the protocol. RTS is always assert-
ed whenever the SCC is enabled.
RSYN—Receive Synchronization Timing (Valid for a Totally Transparent Channel Only)
0 = Normal operation.
1 = If CDS = 1, then the CD pin should be asserted on the second bit of the receive
frame, rather than the first. This configuration matches the behavior of the
MC68302 totally transparent receiver when its EXSYN bit is set; it is included on
the QUICC for compatibility.
EDGE—Clock Edge
The EDGE bits determine the clock edge used by the DPLL for adjusting the receive sam-
ple point due to jitter in the received signal. The selection of the EDGE bits is ignored in
the UART protocol or the x1 mode of the RDCR bits.
00 = Both the positive and negative edges are use for changing the sample point (de-
fault).
01 = Positive edge. Only the positive edge of the received signal is used for changing
the sample point.
10 = Negative edge. Only the negative edge of the received signal is used for changing
the sample point.
11 = No adjustment is made to the sample points.