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ENR - Enable Receiver
When ENR is set, the receiver is enabled. When it is cleared, the receiver
is disabled, and data is not transferred into the receive data register. If ENR
is cleared during data reception, the receiver aborts the current character.
To restart reception, the ENTER HUNT MODE command should be issued
before ENR is set again.
ENT - Enable Transmitter
When ENT is set, the transmitter is enabled; when ENT is cleared, the
transmitter is disabled. If ENT is cleared, the transmitter will abort any data
transmission, clear the transmit data FIFO and shift register, and force the
TXD line high (idle). Data already in the transmit data register will not be
transmitted.
The STOP TRANSMIT command additionally aborts the current frame and
would normally be given to the channel before clearing ENT. The command
does not clear ENT automatically. In a similar manner, to restart trans-
mission, the user should issue the RESTART TRANSMIT command and
then set ENT. The command register is described in 4.3 COMMAND SET.
The specific actions taken with each command vary somewhat according
to protocol and are discussed in each protocol section.
MODE1-MODEO- Channel Mode
OO=HDLC
01 =Asynchronous (UART and DDCMP)
10 =Synchronous DDCMP and V.110
11 = BISYNC
4.5.4 SCC Data Synchronization Register (DSR)
4-24
Each SCC has a DSR used only forthe synchronous protocols (HDLC, BISYNC,
DDCMP, and V.110). Each DSR is a 16-bit, memory-mapped, read-write reg-
ister. DSR specifies the pattern used in the frame synchronization procedure
of the SCC. After reset, the DSR defaults to $7E7E (two FLAGs); thus, no
additional programming is necessary for the HDLC protocol. For BISYNC,
DDCMP, and V.110, the contents of the DSR should be written before the
channel is enabled.
15
8 7
0
SYN2
SYNl
MC68302 USER'S MANUAL
MOTOROLA
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