1176/EXP2 HIT EXPANDER

IMPROVES THE PERFORMANCE OF ECL MULTIHIT TDCs AND SCALERS


The LeCroy VME Model 1176/EXP2 Hit Expander is a companion module to the VME Model 1176 and the CAMAC Models 2277 and 3377, as well as the FASTBUS Models 1876, 1877 and 1877S Time Digitizers. These new TDCs have 1 nsec or better resolution, double hit resolutions better than 20 nsec, a full scale of at least 32.7 �sec and have a 16 hit deep pipeline for each channel. When used with any of these expanders, these TDCs experi ence an improved double pulse resolution (to 2 nsec) and the pipelined hit depth is increased to at least 64 hits per input. This is accomplished by routing one input signal to several TDC channels, creating a composite TDC channel with improved performance. The expander can also be used in a stand-alone mode as a prescaler or a rate reducer with a divide by 8.

FUNCTIONAL DESCRIPTION

Modes of Operation

When used with the 1176, 1876, 1877, 1877S, 2277 or 3377 TDCs, the 1176/EXP2 has two operating modes controlled by a front panel switch.

MODE 1

With the switch in the L.E. ONLY (leading/rising edge only) position, the combined modules (Expander and TDC) form a two input, rising edge only, composite TDC having the same resolution as the TDC module. A set of 7 flip -flops for each channel divide the incoming pulse stream by 8, and drive 8 inputs of the TDC module. The TDC module must be set to record rising edges only. This gives each input a depth of 128 pulses (hits). The double hit resolution is 2 nsec.

MODE 2

With the switch in the L.E.-T.E. (leading/rising-trailing/falling edge) position, the combined modules have only a single input, with both rising and falling edge detection. The TDC module must be set for rising edge recording only. This gives an input with a depth of 128 pulses (256 hits). The double hit resolution is 2 nsec.

Operating Conditions

The 1176/EXP2 maximum input pulse rate is greater than 450 MHz, typically 500 MHz. The same-edge double hit resolution is 2 nsec, and the minimum width is 1 nsec. The EXP2 uses another layer of flip-flops and a faster logic family to achieve the higher speed.

The 1877, 1877S and 3377 will correctly record a long pulse train at the maximum rate. The 2277, 1176 and 1876 will record a short burst at the maximum rate, but the long term average rate must be less than 1/2 of the maximum rate.

Readout

When the data are read from any of the TDC modules, there are 96, 32 or 16 channel numbers, not 8, 4, 2 or 1. The simplest way to deal with this is to mask the 3 least significant bits of the channel number, treating channels 0 through 8 as channel 0 for example. Then sort all of the data for this new composite channel 0 into time order. For the EXP2, the TDC module channels 0-7 are the leading edge, channels 8-15 are the trailing edge.

VME Control

This module uses the respective crates for power and mechanical support only. There are no VME commands required for operation. There is no clear; the modules are free running.

 

SPECIFICATIONS

 
  1176/EXP2 2277/EXP 2277/EXP2
 
Number of Inputs 1 or 2 depending on the mode selected. With mode 1, 2 inputs each with 128 leading edges recorded. In mode 2, 1 input with 128 leading and 128 trailing edges recorded. 4 or 8 depending on the mode selected. With mode 1, 8 inputs each with 64 leading edges recorded. In mode 2, 4 inputs with 64 leading and 64 trailing edges recorded. 2 with 128 leading and trailing edge capacity (128 pulses, measuring both leading and trailing edge).
 
Inputs 2 front panel Lemo connectors, 50 ohm for fast NIM signals, ORed with 2 front panel 2-pin headers for differential ECL, 100 ohm; 2 NIM (50 ohm Lemo) to differential ECL converters are provided for convenient operation with the 1176, 2277, 3377, 1876,1877, or 1877S TDCs. 110 ohm, differential ECL levels; 34-pin header. 2 front panel Lemo connectors, 50 ohm for fast NIM signals, ORed with 2 front panel 2-pin headers for differential ECL, 100 ohm; 2 NIM (50 ohm Lemo) to differential ECL converters are provided for convenient operation with the 1176, 2277, 3377, 1876,1877, or 1877S TDCs.
 
Double Pulse Resolution 2 nsec 5 nsec 2 nsec
 
Minimum Width < 1 nsec < 2.5 nsec < 1 nsec
 
Outputs Differential ECL, designed to match the 1176, 2277, 3377, 1876, 1877 or 1877S. Differential ECL, designed to match the 1176, 2277, 3377, 1876 1877 or 1877S. Differential ECL, designed to match the 1176, 2277, 3377, 1876, 1877 or 1877S.
 
Mode Select Switch in L.E. only position is mode 1 (2 inputs). Switch in L.E. - T.E. only position is mode 2 (1 input). Jumper across the 17th pair of the input connector selects mode 1 (8 input). Without the jumper, the unit is in mode 2 (4 inputs). N/A
 
Propagation Delay 6 nsec typical 8 nsec typical 6 nsec typical
 
Channel-to-Channel Variation < 1.5 nsec < 2 nsec < 1.5 nsec
 
CAMAC/VME VME is used as a power source only. CAMAC is used as a power source only. CAMAC is used as a power source only.
 
Power 1.9 A at +5 V 1.7 A at -6 V 2.4 A at -6 V, 0.1 A at +6 V

 

Some input and output examples for the expander modules.



Copyright� March 1997. LeCroy is a registered trademark of LeCroy Corporation. All rights reserved. Information in this publicaction supersedes all earlier versions.