Agilent Technologies L4400 manual Synchronous Handshake Mode

L4450A 64-Bit Digital I/O with Memory and Counter 8

Synchronous Handshake Mode

In the synchronous handshake mode, a strobe or clock signal is used to transfer data to or from an external device. The strobe line (H1) is an output and is pulsed once for each transfer.

Synchronous Unbuffered Inputs For synchronous handshake unbuffered inputs the H0 line indicates the direction of the transfer. This line is set high to indicate an input operation. The H0 line will remain in the high state until the L4450A direction is changed. The H1 line is the strobe output line. The H2 line is not used and is set to high impedance.

The timing of the input operation is controlled by the TCYCLE parameter set using the CONFigure:DIGital:HANDshake:RATE command. This setting

affects strobe width, memory clock rate, as well as the setup and hold times. Alternatively, the reciprocal form of the command CONFigure:DIGital:HANDshake:CTIMe can be used to specify the speed in

terms of time instead of a rate. TCYCLE begins when the L4450A executes one of the input commands.

The timing should be set such that the device sending the data ensures the

data lines are valid prior to TSETUP time. The trailing edge of the strobe line indicates the L4450A will latch the data within the THOLD time. TSETUP is 90 ns and THOLD is 0 ns. Since THOLD = 0 ns, the sending device can use the trailing edge of the strobe to initiate a change in the data lines.

A synchronous unbuffered input is shown in the diagram below (default handshake line polarity).

H0 (Direction)
	TCYCLE
TCYCLE / 2	TCYCLE / 2
H1 (Strobe)
		TSETUP	THOLD
Data In	Don't-Care	Valid	Don't-Care

For example, the following SCPI commands set the L4450A to have a 16- bit input using synchronous handshake. Two data inputs are then performed and the strobe line is pulsed for each query. The I/O direction line is set high following the first SENSe:DIGital:DATA:WORD? query and remains high until the digital channel is reset or reconfigured.

CONF:DIG:WIDT WORD, (@1101)

CONF:DIG:DIR INP, (@1101)

CONF:DIG:HAND SYNC, (@1101)

SENS:DIG:DATA:WORD? (@1101)

SENS:DIG:DATA:WORD? (@1101)

L4400 User’s Guide 205