Data Transfer; Handshake Timing - HP 5340A Operating And Service Manual

Model 5340A
Installation and Remote Programming
SEQUENCE REQUIREMENTS OF THE THREE WIRE HANDSHAKE
I
I
EVENTS
Listener becomes ready to accept data.
:
Talker has put data on the lines.
:
Talker indicates data is valid.
:
Listener has accepted the data and no longer requires it held valid.
:
Talker indicates the data is no longer valid and may change it.
:
Listener indicates it is ready for new data and a new cycle begins
:
(equivalent to to).
Time data is put on lines before DAV is set low.
:
*A composite of the DIOl through D107 lines for illustrative purposes.
(The curved lines indicate interlocked signal sequence.)

2-25. Data Transfer

2-26. Transfer of data on the bus is asynchronous. It places no restrictions on the data rates of
instruments connected to the bus.
shake lines DAV, RFD, and DAC. The TALKER (sender of data) drives DAV (Data Valid) and the
LISTENER (acceptor of data) drives both RFD (Ready for Data) and DAC (Data Accepted).
The transfer of a byte is initiated by the LISTENER signifying it is ready for data by setting
2-27.
RFD high. When the TALKER recognizes RFD is high and has placed valid data on the data lines
it DAV low. When the, LISTENER senses that DAV is low and is finished using the data, it
sets
sets DAC high. Notice that tpe assertive or action state of both RFD and DAC is high. Since all
instruments on the bus have their corresponding lines connected together (e.g., RFD), all
LISTENERS must be iq a'high state before that line goes high. This wire-AND situation allows
a TALKER to recognize when the slowest listener has accepted a byte of data and is ready for the
next byte.
2-6
Figure 2-1. Handshake Timing
I
I I
The timing and levels required to transfer a byte of infor-
I
I
I
I