Product Summary
The 1785-L40L standard processor from Rockwell Automation coordinates up to 2048 I/O points with 48 kilowords of battery-backed memory. This unit draws 3.3A at 5V DC and supports extended local I/O links for flexible field device control.
Step-by-Step User & Installation Guide
Install the 1785-L40L in the leftmost slot of a 1771 I/O chassis. The controller draws 3.3A backplane current at 5V DC and dissipates 17W of heat. Ensure the power supply can handle this load.
You must connect the extended local I/O port using a compatible adapter. This setup allows scanning up to 16 extended local chassis. Use only Bulletin 1771, 1794, 1746, or 1791 I/O modules.
Configure the dual communication port for Data Highway Plus or Remote I/O. The port supports remote I/O adapter or scanner mode. Set the baud rate to 57.6, 115.2, or 230.4 kbits/s.
Assign I/O hardware addresses using half-slot, single-slot, or double-slot mode. Half-slot mode handles any mix of 8, 16, and 32-point modules. Single-slot mode pairs 32-point modules into two slots.
Verify voltage isolation between communication ports and the relay cartridge. The controller withstands 500V and 1000V tests for 60 seconds. Maintain ambient temperature between 0°C and 60°C.
Deep-Dive Technical FAQ
Q: How do I back up the program on the 1785-L40L?
A: Use EEPROM modules 1785-ME16, -ME32, -ME64, or -M100. The controller supports Battery-Backed Static RAM for runtime storage.
Q: What is the maximum number of I/O racks this processor can coordinate?
A: It supports up to 16 I/O racks and coordinates a total of 61 I/O chassis. The extended local link handles 16 chassis.
Q: Can I use intelligent I/O modules with this controller?
A: Yes, it supports intelligent Bulletin 1771, 1794, 1746, and 1791 modules. These include 8, 16, 32, and specialty modules.
Q: What is the scan time per rack at different baud rates?
A: Local extended scan is 0.5 ms. Remote scans: 10 ms at 57.6 kbits/s, 7 ms at 115.2 kbits/s, and 3 ms at 230.4 kbits/s.
Q: Does the controller include a relay cartridge?
A: It supports the optional 1785-RC Relay Cartridge. The cartridge provides isolated relay outputs for critical control signals.
