Servicing Personal Computers, 3rd Edition

174 Servicing Personal Computers

WR DATA Output. Composite write data.

UNSEP DATA Input. Inverted signal comprising data and clock.

DATA Input signal derived from either a phase-locked oscillator or a monostable (depending

WINDOW upon the state of the PLO/SS line) and is used in the data separation process, see

Figures 4.34 and 4.35.

UNSEP DATA

DATA WINDOW

ΜΓ-

J \_l \ / L·..

Figure 4.34. Data window timing for Figure 4.32

B

C i i D | ! C

UNSEP DATA

DATA WINDOW

ΛΪΓ"

ΓΛ

Figure 4.35. Data window timing for Figure 4.33

PLOC Output. This line goes high when the 8271 has attained data synchronization by

detecting two bytes of zero followed by an expecte ...