Agilent Technologies L4400 manual H0 Direction Data Out

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

Synchronous Unbuffered Outputs For synchronous handshake unbuffered outputs, the H0 line indicates the direction of the transfer. This line is set low to indicate an output operation. The H0 line will remain in the low state until the L4450A direction is changed. The H1 line is the strobe output line.

When the L4450A executes an output command, it sets the data lines and

waits for TCYCLE/2 before asserting the strobe line. The leading edge of the strobe indicates the data is valid. The strobe line is asserted for TCYCLE /2 and then de- asserted. The H2 line is not used and is set to high impedance.

The timing of the output 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. The timing should be set such that the device receiving the data can read the data lines during the TCYCLE/2 time.

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

H0 (Direction)

Data Out Invalid Valid

TCYCLE

TCYCLE / 2 TCYCLE / 2

H1 (Strobe)

For example, the following SCPI commands set the L4450A to have a 16- bit output using synchronous handshake. Two data outputs are then performed and the strobe line is pulsed for each. The I/O direction line is set low following the first SOURce:DIGital:DATA:WORD command and remains low until the digital channel is reset of reconfigured.

CONF:DIG:WIDT WORD, (@1101)

CONF:DIG:DIR OUTP, (@1101)

CONF:DIG:HAND SYNC, (@1101)

SOUR:DIG:DATA:WORD #hFFFF, (@1101)

SOUR:DIG:DATA:WORD #h4DB5, (@1101)

206 L4400 User’s Guide