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The Model 1821 is a programmable FASTBUS Master designed to provide operations on the Segment at the full speed of the standard. The device can be programmed to act as a Slave, a Master or as a Snoop. The 1821 is divided into two sections, the Sequencer and the Interface.

The Sequencer within the 1821 operates under the micro-code control, executing one instruction every 33 nsec. The instructions have multiple fields, typically allowing five operations to be performed at once. The unit offers complete exercise of the FASTBUS protocol lines allowing any FASTBUS operation or series of operations to be programmed. The program word includes a branch operation based upon a wide variety of possible conditions including SS codes, MS codes and the data on the AD lines. This branching feature allows the Model 1821 to execute programs with loops. The Sequencer offers complete FASTBUS arbitration logic. It also provides hard ware for a sparse data scan based upon the T-pins.

Data my be written to the FASTBUS AD lines either from the sequencer or from the Interface Port. Data may also be read from the AD lines and either used by the Sequencer or transmitted to the Interface Port. The sequencer does not provide arithmetic operations on the data.


The Interface of the Model 1821 provides hardwired pedestal subtraction and threshold comparison. Both fea tures can be enabled by the Host computer. The Interface includes an 8K x 10 pedestal memory and a 4K x 32 data memory. Data from the Sequencer may be pipeline processed at a 10 megaword/sec rate. The information is applied at the FASTBUS Auxiliary Connector as it is loaded into the data memory. In this way, the Host can address the data memory, or data-words may be pipeline transferred out of the 1821 to another device such as the 1190 VME Memory Module.

The Interface can be connected to an intelligent Host with an interface personality card. A front-panel Interface Port connector on the Model 1821 provides for connection to a CAMAC Interface, Model 2891A, to the Model 1691B IBM PC/AT Interface or to the Model 1131 VME Interface. For details on interconnection, see LeCroy Application Note AN-28C.

The 1821 may be user programmed. However, firmware within the unit allows the most common FASTBUS primitives and macros to be executed by simple calls from the Host. Many operations can be executed by a single call. The 1821 also provides for executable lists.

Extensive software is available for the Model 1821. Software drivers are available for the VMS and RT11 DEC operating systems. Another software package for the IBM PC/AT or compatible is also available. The LeCroy Interactive FASTBUS Software Toolkit (LIFT) provides an interactive display for the execution and devel opment of user software and firmware from an IBM PC/AT.

The Model 1821 has sockets for eight PROMs. Any one of the PROMs may be loaded into the Sequencer's memory under control of the host computer in < 1 msec. Thereafter, any of the routines in the PROM may be called and executed.

Control words transferred from the Host to the 1821 are used for setup. This allows data compaction and pedestal subtraction to be enabled, it allows Sequencer programs or firmware to be uploaded or downloaded to or from the Host or from the Menu PROMs.



Personality Connector: Uses FASTBUS Auxiliary Connector. Intended for interface to the Host. TTL logic. Provides 16-bit data field, 3-bit address and two strobes; read and write. Access time < 300 nsec. Also 32-bit data in/out field presented at rates up to 10 MHz. See the I/O Circuit Diagram.

Sequence Monitor: Front panel 34-pin ECL connector. Provides monitor of the operation of the Sequencer.

Interface Port: Front panel 34-pin header providing TTL signals to monitor the Interface. Connects to the 2891A, the 1131 or the 1691B.

IN1, IN2, IN3: Differential ECL inputs via 2-pin ECLine connectors. Used as real time conditions for the 1821 Sequencer. Operations depend upon software. Minimum duration 30 nsec.

OUT1, OUT2, OUT3: Differential ECL outputs via 2-pin ECLine connectors. Driven under software control.


Packaging: Standard double-width FASTBUS module in conformance with the FASTBUS Specification ANSI /IEEE-960, 1986.

Power Requirements: 5 A at +5 V; 13 A at -5.2 V; 7 A at -2 V.


Model 1131 - VME-SIB Interface.

Model 1691B - IBM PC/AT Interface.

Model 2891A - CAMAC Interface.

Model DC4/34-m - Connecting cable for 2891A; Here m is length in meters.

Model 1821/DEC - Personality card for DR11W series UNIBUS Interface.

Model 1821/ECL - Personality card for ECLine for connection to ECL triggering system and FASTBUS memories.

Model 1821/MON - 1821 Sequencer Monitor.

Model 1821/VAX - VMS Drivers for VAX and the 1821/DEC.

Organization Diagram

I/O Circuit Diagram

Simplified Block Diagram

Sequencer Block Diagram


The Model 1821 Segment Manager/Interface (SM/I) can be used with a variety of host computers, interfaces and standards.

1821/MON Debug Unit

The 1821/MON is a small hand-held instrument which plugs into the sequencer monitor connector on the 1821 front panel via a 34-pin flat ribbon cable. The 1821/MON displays the current sequencer address and the state of the internal DATABUS on a built-in 4-digit hexadecimal display. Continuous operation, single step, break point, and externally clocked operation may be selected, allowing the user to quickly verify or debug sequencer codes. The 1821/MON is a "must" for all 1821 users doing serious microcode development work.

2891A CAMAC Interface

The 1821 SM/I can be interfaced to CAMAC via the Model 2891A CAMAC Interface. The Model 2891A is con nected to the 1821 SM/I via the front-panel Interface Port providing control and data transfers at the maximum speed of the CAMAC system's host computer (approximately 2 MB/sec). For faster data transfer rates (up to 20 MB/sec), the 1821 SM/I may be directly connected to the Model 4302 CAMAC Triple Port Memory using the 1821/ECL interface card and the ECL bus.

1821/DEC UNIBUS/QBUS Interface

The 1821/DEC connects the 1821 SM/I to the Digital Equipment Corporation (DEC) family of computers. The 1821/DEC mates to the DEC UNIBUS found in PDP-11 and VAX machines via the DEC DR11-W card (or equiva lent). For QBUS-based systems, such as the LSI-11, the PDP-11/23, and the MicroVAX family of computers, the MLSI-DR11-W PLUS card available from MDB Systems Inc. connects directly to the 1821/DEC. The 1821/DEC personality card supports the highest allowed DEC transfer rates via the DR11-W (or compatible) cards (500 kb /sec in DMA mode), and the maximum cable length as recommended by DEC (50 ft or 15 m). However, success ful operation has been achieved at LeCroy with up to 100 ft (30 m) of cable.

1821/VAX Device Drivers

The 1821/VAX provides the software interface between the 1821 SM/I and either the VAX or MicroVAX family of computers including the MicroVAX I, MicroVAX II, the VAX 11/780, and the VAX 8600. The 1821/VAX package utilizes the DR-11 to 1821/DEC interface.

1691B IBM PC/XT/AT Interface

The Model 1691B IBM Interface provides the user with an interface to the 1821 SM/I for IBM PC/XT/AT comput ers and IBM compatibles. It is a card that plugs into a single slot in the PC bus and connects to the 1821 SM/I via the front panel Interface Port.

LIFT (LeCroy Interactive FASTBUS Toolkit)

A software package written in the C language, LeCroy Interactive FASTBUS Toolkit (LIFT), is also available for IBM ATs and compatibles. This software provides the user with user-callable subroutines that can communicate with modules on the FASTBUS segment. A symbolic macro assembler, SONIC, for use with programming the 1821 SM/I in microcode is also provided.

1821/ECL ECLine Interface

The 1821/ECL is a personality card which adapts the 1821 SM/I's auxiliary data and control bus to the LeCroy ECL bus. ECL bus compatible modules include the ECLine Programmable Trigger and Data Handler Units, the FERA Fast ADC System, the PCOS III MWPC System, and the LeCroy VME Model 1190 Memory. These mod ules can be used with the 1821 SM/I via the 1821/ECL providing data rates up to 40 MB/sec. The 1821/ECL also provides a second SM/I Interface Port which may be used as a diagnostic connection for a local processor.

1131 VME List Processing Interface

The Model 1131 List Processing VME Interface provides an interface between VME and the FASTBUS segment via the front-panel, high-speed Systems Interface Bus (SIB) Interface Port on the 1821 SM/I. See separate data sheet.

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