{"product_id":"allen-bradley-1785-lt3-plc-5-classic-processor-module","title":"Allen-Bradley 1785-LT3 PLC-5 Classic Processor Module","description":"\u003ch2\u003eAllen-Bradley 1785-LT3 PLC-5 Classic Processor Module\u003c\/h2\u003e\n\u003cp\u003eConfigured for high-speed logic execution and industrial control in PLC-5 local and remote I\/O chassis, the \u003cstrong\u003eAllen-Bradley 1785-LT3\u003c\/strong\u003e, also cataloged as the \u003cstrong\u003e1785-LT3\u003c\/strong\u003e PLC-5 Classic Processor Module, provides direct physical and electrical execution of user programs up to 6K words SRAM capacity.\u003c\/p\u003e\n\u003ch3\u003eHardware Specifications\u003c\/h3\u003e\n\u003cfigure class=\"table\"\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003e\u003cstrong\u003eParameter\u003c\/strong\u003e\u003c\/th\u003e\n\u003cth\u003e\u003cstrong\u003eSpecification\u003c\/strong\u003e\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eModel\u003c\/td\u003e\n\u003ctd\u003e1785-LT3\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBrand\u003c\/td\u003e\n\u003ctd\u003eAllen-Bradley\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOrigin\u003c\/td\u003e\n\u003ctd\u003eUSA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eWeight\u003c\/td\u003e\n\u003ctd\u003e3.19 lbs\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eOperating Temp\u003c\/td\u003e\n\u003ctd\u003e0 to 60 deg C\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePower Consumption\u003c\/td\u003e\n\u003ctd\u003e12.5 W\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBackplane Requirement\u003c\/td\u003e\n\u003ctd\u003e2.5 A at 5 VDC\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eUser Memory\u003c\/td\u003e\n\u003ctd\u003e6K words SRAM (supports optional 8K EEPROM)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMax Total I\/O\u003c\/td\u003e\n\u003ctd\u003e512 I\/O points\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMax Analog I\/O\u003c\/td\u003e\n\u003ctd\u003e256 \/ 3072 depending on rack distribution\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eProgram Scan Time\u003c\/td\u003e\n\u003ctd\u003e8 ms per 1000 words (typical)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCommunication Ports\u003c\/td\u003e\n\u003ctd\u003eDH+ Channel, Remote I\/O Channel, RS-232-C\/422-A\/423-A\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eI\/O Scan Time\u003c\/td\u003e\n\u003ctd\u003e10 ms at 57.6 kbps, 7 ms at 115.2 kbps, 3 ms at 230.4 kbps\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMax Universal Remote Chassis\u003c\/td\u003e\n\u003ctd\u003e32 max per I\/O link\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/figure\u003e\n\u003ch3\u003eBackplane Bus Communication Velocity \u0026amp; Network Execution\u003c\/h3\u003e\n\u003cp\u003eThe \u003cstrong\u003e1785-LT3\u003c\/strong\u003e interfaces directly via the 1771 backplane bus, delivering deterministic backplane bus communication velocity across local and remote rack assemblies. The integrated Data Highway Plus (DH+) and Remote I\/O (RIO) channels maintain cycle synchronization with industrial communication networks. Firmware execution routines manage real-time I\/O scan intervals, enabling dynamic backplane power distribution and determinism during multi-chassis rack updates without data corruption.\u003c\/p\u003e\n\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\n\u003cp\u003eQ: What is the backplane power allocation required for the 1785-LT3 module?\u003c\/p\u003e\n\u003cp\u003eA: The module requires 2.5 A at 5 VDC from the 1771 backplane power supply.\u003c\/p\u003e\n\u003cp\u003eQ: How does the communication rate on the Remote I\/O channel impact rack scan time?\u003c\/p\u003e\n\u003cp\u003eA: I\/O scan time per rack varies based on baud rate: 10 ms at 57.6 kbps, 7 ms at 115.2 kbps, and 3 ms at 230.4 kbps.\u003c\/p\u003e\n\u003cp\u003eQ: Can the internal SRAM memory be backed up non-volatilely on the processor?\u003c\/p\u003e\n\u003cp\u003eA: Yes, the module supports an optional EEPROM module with a maximum memory capacity of 8K words to store user applications permanently.\u003c\/p\u003e\n\u003ch3\u003eField Installation Guidelines\u003c\/h3\u003e\n\u003col\u003e\n\u003cli\u003eEnsure main backplane power is disconnected before installing or removing the module from the 1771 I\/O chassis.\u003c\/li\u003e\n\u003cli\u003eAlign the printed circuit board card guide with the top and bottom slots of the designated processor slot.\u003c\/li\u003e\n\u003cli\u003eSlide the module firmly into the chassis until the backplane connector fully engages.\u003c\/li\u003e\n\u003cli\u003eSecure the module retaining latch at the top and bottom of the chassis frame to maintain earth grounding continuity and prevent vibrational displacement.\u003c\/li\u003e\n\u003cli\u003eTerminate DH+ and RIO communication cables using recommended twinaxial shielded cables, ensuring proper termination resistors (150 ohm or 82 ohm depending on baud rate) are installed across the network ends.\u003c\/li\u003e\n\u003cli\u003eConnect shield drain wires to designated chassis ground points to minimize EMI\/RFI noise interference.\u003c\/li\u003e\n\u003c\/ol\u003e","brand":"Allen-Bradley","offers":[{"title":"Default Title","offer_id":43755469996122,"sku":"1785-LT3","price":123.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0612\/4601\/3530\/files\/1785-LT32.jpg?v=1785305057","url":"https:\/\/www.plcmasters.com\/products\/allen-bradley-1785-lt3-plc-5-classic-processor-module","provider":"PLC Masters Ltd.","version":"1.0","type":"link"}