Freescale Semiconductor, Inc.
When SCPEN comes low again, the next eight rising edges of SCPCLK shift data in from
SCP Rx. This data is then stored in the selected byte. Figure 5鈥? illustrates this process.
SCPEN
SCPCLK
SCP Rx
DON鈥橳 CARE R/W
A3
A2
A1
A0
DON鈥橳 CARE
D7
D6
D5
D4
D3
D2
D1
D0
DON鈥橳 CARE
Freescale Semiconductor, Inc...
SCP Tx
HIGH IMPEDANCE
Figure 5鈥?. Serial Control Byte Register Write Operation Double 8鈥揃it Transaction
5.2.5
SCP Merged Read/Write
Merged operations are accomplished by not taking SCPEN high between separate SCP instructions.
The SCP bytes/nibbles are strung together in a continuous bit stream and can be a mux or read/write
command. The device is able to extract the separate instructions and provide the appropriate response.
The SCPEN signal goes low at the start of the bit stream and goes high again at the end.
Figure 5鈥? illustrates this process with two consecutive nibble register read operations. The merged
instructions can be a free mix of nibble/byte/read/write operations.
SCPEN
SCPCLK
SCP Rx
DON鈥橳 CARE
R/W A2
A1
A0
DON鈥橳 CARE
R/W
A2
A1
A0
DON鈥橳 CARE
HIGH
IMPEDANCE
SCP Tx
HIGH IMPEDANCE
D3
D2
D1
D0
HIGH
IMPEDANCE
D3
D2
D1
D0
NOTES:
1. R/W = 1 for a read operation.
2. Data is shifted out on SCP Tx on the falling edges of SCPCLK, MSB first.
3. Data is shifted into the chip from SCP Rx on the rising edges of SCPCLK, MSB first.
Figure 5鈥?. Merged Serial Control Port Nibble Register Read Operation
MOTOROLA
MC145574
For More Information On This Product,
Go to: www.freescale.com
5鈥?