MC145745FW 查看數據表（PDF） - Motorola => Freescale

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MC145745FW

V.21/V.23 Telemeter Modem

Motorola => Freescale 

SCPEN

ÎÎÎÎ SCPCLK

ÎÎÎÎÎÎÎÎÎÎÎÎ SCP Rx

R/W A2 A1 A0

ÎÎÎÎÎ DON’T CARE

ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ DON’T CARE

SCP Tx

HIGH IMPEDANCE

D3 D2 D1 D0

Figure 5. Serial Control Port Read Operation

SCPEN

ÎÎÎÎ ÎÎÎÎÎ SCPCLK

ÎÎÎÎÎÎÎÎÎÎÎÎ ÎÎÎÎÎÎÎÎÎÎÎÎÎÎÎ SCPRx

DON’T CARE

R/W A2 A1 A0 D3 D2 D1 D0 DON’T CARE

SCP Tx

HIGH IMPEDANCE

Figure 6. Serial Control Port Write Operation

DESCRIPTION OF THE SCP TERMINAL

The SCP bus is made up of the following four pins.

SCP Tx (Pin 20)

The SCP Tx pin outputs the control, status, and data in-

formation from the 4–bit wide register. During the read action

transaction, a R/W bit and the three address bits are shifted

in from SCP Rx at four SCPCLK rising edges, subsequent to

SCPEN going low. After this, if a read operation is selected,

SCP Tx comes out of the high impedance state at the first

falling edge of SCPCLK, and outputs the first bit (MSB) of the

chosen register. The remaining three bits of the chosen reg-

ister are shifted out from SCP Tx at the following three

SCPCLK falling edges. After the last bit (LSB) is shifted out,

SCPEN must return to high. Then SCP Tx returns to the high

impedance condition.

SCP Rx (Pin 21)

The SCP Rx pin is used to input control and data informa-

tion into the 4–bit wide register. Data is shifted in from

SCP Rx at SCPCLK rising edge, while SCPEN is low. The

first bit is the R/W bit (1 = read, 0 = write), and the next three

bits address one of seven byte–registers. The address bits

are shifted in MSB first. If the write action is chosen, the 4–bit

data is shifted in from SCP Rx at the next four SCPCLK rising

edges. If the read action is chosen, 4–bit data in the selected

register is shifted out on SCP Tx. SCP Rx is ignored while

SCPEN is high.

SCPCLK (Pin 22)

The SCPCLK pin is an input of standard clock for hand-

shaking between SCP and MCU. After SCPEN comes low

and the SCP transaction occurs, data is shifted from SCP Rx

into the device at the rising edge of SCPCLK, and is shifted

out on SCP Tx at the falling edge of SCPCLK. When SCPEN

is high, SCPCLK is ignored (i.e., it may be continuous or it

can operate in the burst mode).

SCPEN (Pin 23)

When the SCPEN pin is held low, the SCP transaction is

enabled and control, status, and data information is trans-

ferred. If SCPEN is returned to high, the SCP action in prog-

ress is aborted, and the SCP Tx pin enters a high impedance

condition.

MC145745

10

MOTOROLA

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