{"product_id":"allen-bradley-1785-lt-2a-plc-5-25-processor-module","title":"Allen-Bradley 1785-LT-2A PLC-5\/25 Processor Module","description":"\u003ch2\u003eAllen-Bradley 1785-LT-2A PLC-5\/25 Processor Module\u003c\/h2\u003e\n\u003cp\u003eConfigured for medium-scale industrial automation in Allen-Bradley 1771 chassis systems, the \u003cstrong\u003eAllen-Bradley 1785-LT-2A\u003c\/strong\u003e (\u003cstrong\u003e1785-LT-2A\u003c\/strong\u003e PLC-5\/25 Processor Module) provides direct physical\/electrical execution.\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-LT-2A\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\u003e1.8 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\u003eBackplane current defined by 1771 chassis supply\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eArchitecture\u003c\/td\u003e\n\u003ctd\u003ePLC-5 Classic family\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMemory\u003c\/td\u003e\n\u003ctd\u003e13K words SRAM (expandable to 17K or 21K words)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eDigital\/Analog I\/O Support\u003c\/td\u003e\n\u003ctd\u003e1024 digital I\/O + 1024 analog I\/O points\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMaximum I\/O Capacity\u003c\/td\u003e\n\u003ctd\u003eUp to 3072 total I\/O points\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eChassis Limit\u003c\/td\u003e\n\u003ctd\u003eSupports up to 17 I\/O chassis (16 remote)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eProgram Scan Time\u003c\/td\u003e\n\u003ctd\u003e2 ms per K words (bit logic)\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eCommunication Ports\u003c\/td\u003e\n\u003ctd\u003e1 x DH+ channel, 1 x Remote I\/O channel\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eMounting Location\u003c\/td\u003e\n\u003ctd\u003e1771 I\/O chassis, left-most slot\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 Performance\u003c\/h3\u003e\n\u003cp\u003eThe \u003cstrong\u003eAllen-Bradley 1785-LT-2A\u003c\/strong\u003e executes high-speed backplane exchanges within the 1771 architecture while managing deterministic serial communication link profiles over DH+ and Remote I\/O. Data refresh routines operate at I\/O scan speeds of 10 ms at 57.6 kbps, 7 ms at 115.2 kbps, and 3 ms at 230.4 kbps across expanded 1771 chassis arrays. Firmware memory scaling features support physical SRAM expansions from 13K words up to 21K words without altering backplane timing profiles.\u003c\/p\u003e\n\u003ch3\u003eFrequently Asked Questions\u003c\/h3\u003e\n\u003cp\u003eQ: What specific slot position must the 1785-LT-2A occupy in the 1771 chassis?\u003c\/p\u003e\n\u003cp\u003eA: The module must be installed strictly into the left-most slot (Slot 0) of the primary 1771 I\/O chassis to properly interface with backplane power and system bus signals.\u003c\/p\u003e\n\u003cp\u003eQ: Can the 1785-LT-2A memory be expanded beyond the default 13K words SRAM?\u003c\/p\u003e\n\u003cp\u003eA: Yes, the processor onboard memory is expandable to 17K words or 21K words using compatible Allen-Bradley memory expansion hardware modules.\u003c\/p\u003e\n\u003ch3\u003eField Installation Guidelines\u003c\/h3\u003e\n\u003col\u003e\n\u003cli\u003ePower down the 1771 chassis completely before inserting or removing the processor module. Hot-swapping the main CPU is not permitted.\u003c\/li\u003e\n\u003cli\u003eVerify that the 1785-LT-2A is securely aligned with the card guides and fully seated into the left-most slot of the primary 1771 chassis.\u003c\/li\u003e\n\u003cli\u003eTorque all ground connections on the 1771 chassis frame to maintain earth ground continuity and minimize signal noise.\u003c\/li\u003e\n\u003cli\u003eEnsure all DH+ and Remote I\/O communication wiring utilizes properly shielded twisted-pair cables with ground drain wires terminated at one end only.\u003c\/li\u003e\n\u003cli\u003eMaintain at least 50 mm clearance around chassis ventilation slots to prevent thermal buildup within the enclosure.\u003c\/li\u003e\n\u003c\/ol\u003e","brand":"Allen-Bradley","offers":[{"title":"Default Title","offer_id":43755468226650,"sku":"1785-LT-2A","price":123.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0612\/4601\/3530\/files\/1785-LT-2A2.jpg?v=1785304761","url":"https:\/\/www.plcmasters.com\/products\/allen-bradley-1785-lt-2a-plc-5-25-processor-module","provider":"PLC Masters Ltd.","version":"1.0","type":"link"}