HP 3336A - Page 67

Appendix A
The timing diagram illustrates the handshake process by indicating the actual waveforms
on the DAV, NRFD, and NDAC lines. The NRFD and NDAC signals each represent
composite waveforms resulting from two or more Listeners accepting the same data byte
at slightly different times. This is usually due to variations in the transmission path length
and individual instrument response rates (delays).
The flow chart represents the same sequence of events in a different form.
The subscripted letters on the flow chart and the timing diagram refer to the same event
on the list of events.
HANDSHAKE line timing diagram for one talker and multiple listeners using the
handshake process. Two cycles of the handshake sequence are shown. Also refer to the
flow diagram and list of events on this figure.
Ti Te Ts Tats k F Tio Tu Tz Tdie
ae aes !
1a
bo
'
_—
‘
i)
i
O10 LINES :
(ONLY ONE LINE TS
SHOWN AS AN EXAMPLE)
Se ae es oe
data.
Period in which all
listeners accept data.
List of Events for Handshake Process
Source initializes DAV to high (False - data not valid).
Acceptors initialize NRFD to low (True - none are ready for data), and set
NDAC to low (True - none have accepted the data).
Source checks for error condition (both NRFD and NDAC high), then
places data byte on DIO lines.
Source delays to allow data to settle on DIO lines.
Figure 3-A-14. Handshake Timing Relationship.
A-11