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LeCroy's NIM Model 3031 qVt Interface has been designed to allow the Model 3001 qVt Multichannel Analyzer to be remotely controlled from an external computer. Communication with the host computer is accomplished over the LeCroy System Interface Bus (SIB), a high speed parallel bus in use on several LeCroy modules. This bus uses a 60-pin flat cable to connect the 3031 to either a PC-compatible computer or to a VME system. The PC must have a LeCroy Model 1691B card housed in an expansion slot of the PC. With a VME system, an 1131 VME-to-SIB interface is required. The Model 3031 allows the qVt to be used for calibration and setup as well as for display during the operation of an experiment.


Data in the 3001 is organized into 16 bit words. The 3031 allows this memory to be written into from a PC via a 1691B card or from a VME system via an 1131 VME to SIB bus interface. The data in the qVt's memory may be displayed on a standard x-y scope or read out to a computer and plotted on the CRT screen.

Included with the Model 3031 is an example PC program which allows for the reading of data as well as control of most of the qVt's functions. Data from the qVt's memory may be saved to disk in an ASCII format. Previously saved files may be recalled from disk and downloaded to the qVt. This example program is intended only to illustrate methods of programming and will aid in the development of application specific software.

An increment feature allows any channel of the qVt to be incremented by one. This feature allows use of the analyzer as a histogram and display module when used with an x-y scope.

The Model 3031 contains an incrementing address register which may be loaded from the SIB bus. The value contained in the register is used to address memory for both read and write operations. After the read or write operation is performed, the address will be incremented by one providing the auto increment bit is on. This feature is useful when reading the entire memory contents.

Note that the Model 2301 is available to read out the qVt from CAMAC. See the separate data sheet for details.


Model 3031

For use with a PC-compatible host, the LeCroy Model 1691B must be installed. If the host interfaces to a VME system, then the LeCroy Model 1131 must be used in the VME crate.

Inputs and Outputs: Communication from host computer to front-panel SIB port is via a 60-pin high density cable. (This cable is purchased separately with part number DCSIB/60-L, where L = length in feet.) Communica tion with the 44-pin qVt interface connector is implemented using a 60-pin flat cable and a LeCroy 60-pin to 44 -pin convertor card.

General: A sample "C" language program written for a PC is included.


Write 6 bit control word.
D0 ­p; Auto increment. Set the auto increment bit so any read or write cycle to the qVt will increment the address counter by one.

D2 ­p; Start qVt. Arm the qVt for data acquisition.

D3 ­p; Stop qVt. Stop qVt data acquisition.

D4 ­p; Clear qVt. Clear entire qVt memory.

D5 ­p; Increment address. Increment the address register by one.

W1: Write to internal address latch. This address will be used for the next read, write or increment of the qVt.

W2: Write data to the qVt using the address stored in the internal address latch.

W5: Increment the value of the qVt data memory using the address stored in the internal address latch.

W6: Transfer data from the qVt to the 3031's internal data latch using the address stored in the internal address latch. This command is usually followed by an R2 read of the internal data latch.

R0: Read back status of control register.
D0 ­p; Auto increment bit. 1 = Auto increment on.

D2 ­p; Status bit. 1 = qVt in acquisition mode.

D3 ­p; Overflow bit. 1 = qVt has reached terminal count (65535). Overflow bit is latched in the 3031 and cleared when clear qVt is issued.

D4 D7 ­p; Module address. D7 = MSB, D4 = LSB.

R1: Read back value of internal address register.

R2: Read internal data latch. This command is usually preceded by a W6 transfer of data from the qVt to the internal data latch.

R3: Read value of most recent conversion.

Model 1691B

Signal Levels: All connector signals are TTL levels.

Data Format: 16-bit word on data cable, built from two 8-bit host transfers. Bidirectional data is accompanied by four Module Address and four Register Address lines driven from the 1691B to the connected device.

Data Rate: Each transfer is initiated by a positive going TTL strobe from the host. Therefore, the rate is depen dent upon host computer speed and cable length. Typical speed using an 8 MHz, IBM PC-AT driving 2 meters of cable is 2 MB/sec.

Signals: Active low TTL RD, WR, ENB, and BYP for use with the 1821 are driven by the 1691B.

Compatibility: IBM PC compatibles with 80286 or higher performance processors.


Adapter board required when using the 1691B.

DCSIB/60-L: 60-pin, high density cable from the 3031 to the 1691B or 1131. Specify the length in feet (maximum 30 feet).

Copyright© September 1995. LeCroy is a registered trademark of LeCroy Corporation. All rights reserved. Information in this publicaction supersedes all earlier versions.