HP 3336A - Page 68

Appendix A
A-12
T,
T4
Ts
Te
T,
P;
(T;—-T1 0)
Ts *
To
Tio
P,
(T10-Ti2)
Ti
Ti2
Acceptors have all indicated readiness to accept first data byte; NRFD
goes high.
When the data is settled and valid, and the source has sensed NRFD high,
DAV is set low.
First acceptor sets NRFD low to indicate that it is no longer ready, then
accepts the data. Other acceptors follow at their own rates.
First acceptor sets NDAC high to indicate that it has accepted the data.
(NDAC remains low due to other acceptors driving NDAC low).
Last acceptor sets NDAC high to indicate that it has accepted the data; all
have now accepted and NDAC goes high.
Source, having sensed that NDAC is high, sets DAV high. This indicates to
the acceptors that data on the DIO lines must now be considered not valid.
Upon completion of this step, one byte of data has been transferred.
Source changes data on the DIO lines.
Acceptors, upon sensing DAV high set NDAC low in preparation for next
cycle. NDAC goes low as the first acceptor sets it low.
First acceptor indicates that it is ready for the next data byte by setting
NRFD high. (NRFD remains low due to other acceptors driving NRFD
low).
Source checks for error condition (both NRFD and NDAC high), then
places data byte on DIO lines (as at T,).
Source delays to ailow data to settle on DIO lines.
Last acceptor indicates that it is ready for the next data byte by setting
NRFD high; NRFD signal line goes high.
Source, upon sensing NRFD high, sets DAV low to indicate that data on
DIO lines is settled and valid.
First acceptor sets NRFD low to indicate that it is no longer ready, then
accepts the data.
First acceptor sets NDAC high to indicate that it has accepted the data.
Last acceptor sets NDAC high to indicate that it has accepted the data (as
at Ts ).
Source, having sensed that NDAC is high, sets DAV high (as at T;).
Source removes data byte from DIO signal lines after setting DAV high.
Acceptors, upon sensing DAV high, set NDAC low in preparation for next
cycle.
Note that all three handshake lines return to their initialized states, as at
T, and T..