Allen Bradley1771-DBBASIC Module, Dual Serial Ports, RS-232-C and RS-422-A, 1771 I/O Chassis, Series A

Product Description

What this part is

Allen-Bradley 1771-DB BASIC module, Series A Revision A/D. Product Type: intelligent co-processor module for the 1771 I/O platform. Function: runs a user program written in BASIC, providing maths functions, report generation and serial device handling for any Allen-Bradley processor that reaches the 1771 I/O system by block transfer. Programming Language: BASIC. Backplane Current: 1.5 A. Operating Temperature: 0 to 60 °C. Mounting Type: 1771 I/O chassis slot. Unit Quantity: 1 Pc.

Decoding the designation

1771 — the Allen-Bradley 1771 I/O platform, the rack-based I/O family served by PLC-2, PLC-3 and PLC-5 processors.

DB — the BASIC module within that platform, the programmable co-processor as distinct from the 1771-DA ASCII module, which passes characters without running a user program.

Series A — the first hardware revision of the module.

Rev A/D — the firmware revision level carried on this unit.

Communication and memory data

Communication Standard: RS-232-C and RS-422-A serial. Serial Ports: two, a peripheral port for the connected device and a program port for terminal access to the BASIC interpreter. Program Storage: RAM for the working program, EPROM for resident programs. Backplane Current: 1.5 A. Data Transfer: block transfer read and write to the processor data table.

What these specs mean in practice

Programming Language: BASIC. Computation that would take dozens of ladder rungs — floating-point scaling, recipe arithmetic, string handling for a report — is written as a few lines and runs on the module rather than in the processor scan.

Serial Ports: two. One port drives the printer, terminal, modem or third-party controller while the other stays available for editing and monitoring the BASIC program, so a running installation stays reachable.

Program Storage: RAM and EPROM. A program burned into EPROM survives a power cycle and comes back running, which is what makes the module suitable for an unattended report or logging station.

Backplane Current: 1.5 A. That is the largest single draw among common 1771 modules and it dominates the chassis power budget, so an 8 A 1771-P4S supply carries a limited number of them.

Operating Temperature: 0 to 60 °C. The band matches the rest of the 1771 platform, so the module needs no special enclosure provision beyond the rack’s own.

Mounting data

Mounting Type: single slot in a 1771 I/O chassis. Controller Platform: any Allen-Bradley processor communicating with the 1771 I/O system by block transfer, including PLC-2, PLC-3 and PLC-5.

Quantity and configuration

Unit Quantity: 1 Pc. One BASIC module.

Interchange guidance

Manufacturer Status: discontinued. Part Number: 1771-DB. MPN Variants: 1771DB, 1771 DB. The 1771-DA ASCII module occupies the same slot and the same serial world but passes characters rather than running a user program, so it is a related module rather than an equal. Series B of the 1771-DB extends the serial standards and the EPROM capacity, so it is an uprated execution rather than an identical part. Reference documentation: Rockwell publications 1771-6.5.34 and 1771-UM113, BASIC Module User Manual.