MC68000 MOTOROLA [Motorola, Inc], MC68000 Datasheet - Page 399

• Manufacturer Part Number: MC68000
• Manufacturer: MOTOROLA [Motorola, Inc]

PCM highway is any time-division multiplexed serial interface (i.e., data is transferred over
time slots). The most common examples of a PCM highway (serial bus) are a T1 line or a
CEPT line; however, there are many other possible PCM highway configurations. T1 has 24
8-bit channels and is clocked at 1.544 MHz. CEPT has 32 8-bit channels and is clocked at
2.048 MHz. In both cases, the actual rate of an 8-bit channel is 64 kbps. If more data
throughput is needed, multiple 8-bit time slots can be grouped together for faster data trans-
fer. You may wish to choose PCM highway, even if you only have one SCC using the inter-
face (and therefore one long time slot) as will be shown.
Example 1. If you need multiple transparent channels on separate physical interfaces, then
all of them can be NMSI or all but one as NMSI. Thus, you can choose from the following
four combinations:
MOTOROLA
The following examples illustrate how the different types of interfaces can be combined.
1. NMSI1, NMSI2, and NMSI3
2. PCM, NMSI2, and NMSI3
3. IDL, NMSI2, and NMSI3
4. GCI, NMSI2, and NMSI3
OR BRG2
OR BRG3
TCLK2
TCLK3
BRG1
Figure D-22. Multiplexed Modes Example
SCC3
SCC1
SCC2
BRG
BRG
BRG
MC68302 USER’S MANUAL
MC68302
SERIAL CHANNELS
MUX
PHYSICAL I/F
MUX
MSC3 = 1
MSC2 = 1
NMSI2 PINS OR
P I/O IF MUX
IS CHOSEN
NMSI3 PINS OR
P I/O IF MUX
IS CHOSEN
LAYER 1 PINS.
MUX = (IDL, GCI,
OR PCM)
MC68302 Applications
D-49