W167B データシートの表示（PDF） - Cypress Semiconductor

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W167B

133-MHz Spread Spectrum FTG for Pentium® II Platforms

Cypress Semiconductor 

PRELIMINARY

W167B

Signaling Requirements

As shown in Figure 6, valid data bits are defined as stable logic

0 or 1 condition on the data line during a clock HIGH (logic 1)

pulse. A transitioning data line during a clock HIGH pulse may

be interpreted as a start or stop pulse (it will be interpreted as

a start or stop pulse if the start/stop timing parameters are

met).

A write sequence is initiated by a “start bit” as shown in Figure

7. A “stop bit” signifies that a transmission has ended.

As stated previously, the W167B sends an “acknowledge”

pulse after receiving eight data bits in each byte as shown in

Figure 8.

Sending Data to the W167B

The device accepts data once it has detected a valid start bit

and address byte sequence. Device functionality is changed

upon the receipt of each data bit (registers are not double buff-

ered). Partial transmission is allowed meaning that a transmis-

sion can be truncated as soon as the desired data bits are

transmitted (remaining registers will be unmodified). Transmis-

sion is truncated with either a stop bit or new start bit (restart

condition).

SDATA

SCLOCK

Valid

Data

Bit

Change

of Data Allowed

Figure 6. Serial Data Bus Valid Data Bit

SDATA

SCLOCK

Start

Bit

Stop

Bit

Figure 7. Serial Data Bus Start and Stop Bit

11

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