MC68000 MOTOROLA [Motorola, Inc], MC68000 Datasheet - Page 255

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

The SCP can be configured to operate in a local loopback mode, which is useful for local
diagnostic functions.
Note that the least significant bit of the SCP is labeled as data bit 0 on the serial line; where-
as, other devices, such as the MC145554 CODEC, may label the most significant bit as data
bit 0. The MC68302 SCP bit 7 (most significant bit) is shifted out first.
The SCP key features are as follows:
MOTOROLA
• Three-Wire Interface (SPTXD, SPRXD, and SPCLK)
• Full-Duplex Operation
• Clock Rate up to 4.096 MHz
• Programmable Clock Generator
• Local Loopback Capability for Testing
(OUTPUT)
(OUTPUT)
NOTE: Transmitted data bits shift on rising edges; received bits are sampled on falling edges.
NOTE: Transmitted data bits shift on falling edges; received bits are sampled on rising edges.
(INPUT)
(INPUT)
SPRXD
SPRXD
SPCLK
SPTXD
SPTXD
SPCLK
7
7
7
7
MSB
MSB
MSB
MSB
6
6
6
6
Figure 4-44. SCP Timing
MC68302 USER’S MANUAL
5
5
5
5
(a) CI=0
(b) CI=1
4
4
4
4
3
3
3
3
2
2
2
2
Communications Processor (CP)
1
1
1
1
LSB
LSB
LSB
LSB
0
0
0
0
THREE-STATE
THREE-STATE
LOGIC HIGH
LOGIC HIGH
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