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1
2
3
L1TXD
8 BITS 8 BITS 8 BITS
L1RXD
L1CLK
L1SY0
L1SY1
PCM CHANNEL 1 CONTAINS 8 BITS
AND CAN BE ROUTED TO ANY SCC.
NOTE: Whenever the syncs are active, data from that SCC is transmitted and received using L1CLK edges.
Figure 4-10. PCM Channel Assignment on a T1/CEPT Line
4.4.4 Nonmultiplexed Serial Interface (NMSI)
The IMP supports the NMSI with modem signals. In this case, the serial interface connects
the seven serial lines of the NMSI1/ISDN interface (RXD1, TXD1, RCLK1, TCLK1, CD1,
CTS1, and RTS1) directly to the SCC1 controller. NMSI pins associated with SCC2 and
SCC3 can be used as desired or left as general-purpose I/O port pins. See 3.3 Parallel I/O
Ports for an example. RTS is an output of the transmitter, while CTS and CD are inputs to
the transmitter and receiver, respectively. See 4.5.3 SCC Mode Register (SCM) and 4.4 Se-
rial Channels Physical Interface for additional information.
CTS and CD may be programmed to control transmission and reception automatically or to
just generate interrupts.
4.4.5 Serial Interface Registers
There are two serial interface registers: SIMODE and SIMASK. The SIMODE register is a
16-bit register used to define the serial interface operation modes. The SIMASK register is
a 16-bit register used to determine which bits are active in the B1 and B2 channels of ISDN.
4.4.5.1 Serial Interface Mode Register (SIMODE)
If the IDL or GCI mode is used, this register allows the user to support any or all of the ISDN
channels independently. Any extra SCC channel can then be used for other purposes in
MOTOROLA
4
5
6
7
PCM CHANNEL 2 CONTAINS TWO 8-BIT TIME
SLOTS AND CAN BE ROUTED TO ANY SCC.
MC68302 USER'S MANUAL
Communications Processor (CP)
8
9
PCM CHANNEL 3 CONTAINS 10
BITS AND CAN BE ROUTED TO
ANY SCC.
24 OR 32
8 BITS
(CLOCK NOT TO SCALE)
4-19
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