{"product_id":"ab-1785-lt2-programmable-logic-controller-dh-rio-cpu","title":"AB 1785-LT2 Programmable Logic Controller DH+ RIO CPU","description":"\u003ch3\u003eProduct Overview\u003c\/h3\u003e\n\u003cp\u003eThe Allen-Bradley 1785-LT2 functions as a central processing unit within the classic PLC-5 architecture, specifically driving the PLC-5\/25 control assembly. This modular processor coordinates mid-range manufacturing lines, complex sequence operations, and analog chemical dosing processes. It provides 13 Kwords of internal battery-backed Static RAM (SRAM) for stable program execution, with expansion capacity up to 21 Kwords using optional cartridge add-ons. Integrated Data Highway Plus (DH+) and universal Remote I\/O (RIO) scanners enable the module to manage up to 3072 discrete I\/O points and 1024 analog channels across multiple remote chassis clusters. We deliver this computing hardware as a 100% brand new, original factory-sealed unit to ensure mechanical precision and exact firmware timing for legacy system drop-ins.\u003c\/p\u003e\n\u003ch3\u003eTechnical Specifications\u003c\/h3\u003e\n\u003cp\u003eThe following data table maps the electrical inputs, processing speeds, and maximum configuration limits of the 1785-LT2 processor:\u003c\/p\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr class=\"firstRow\"\u003e\n\u003ctd\u003e\u003cstrong\u003eSpecification\u003c\/strong\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cstrong\u003eDetails\u003c\/strong\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eManufacturer\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003eAllen-Bradley \/ Rockwell Automation\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eCatalog Number\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e1785-LT2 (Series A)\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eProduct Line\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003ePLC-5 System\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eCondition\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e100% Brand New Original Factory Sealed\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eModule Type\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003eProgrammable Logic Controller Processor\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eBase Memory Capacity\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e13 Kilowords Static RAM (SRAM)\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eMemory Expansion Limit\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003eUp to 17 or 21 Kilowords\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eMax Total Discrete I\/O\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e3072 Inputs \/ 3072 Outputs (Complementary Mix)\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eMax Analog I\/O Points\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e1024 Inputs \/ Outputs\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eBackplane Current Draw\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e2.5 Amps at 5V DC\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eIntegrated Hardware Ports\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e1 x DH plus Channel, 1 x Remote I\/O Channel, 1 x Serial\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eBit Instruction Scan Time\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003eApproximately 1.0 ms per Kword\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eMax Combined Chassis Racks\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e17 Total Chassis\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eMax Universal Remote Racks\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e16 Racks Maximum\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eRIO Update Time (57.6 kbps)\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e10 ms Per Rack\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eRIO Update Time (115.2 kbps)\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e7 ms Per Rack\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eRIO Update Time (230.4 kbps)\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e3 ms Per Rack\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eBackup Battery Model\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003eAllen-Bradley 1770-XYC Lithium Battery\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eSupported EEPROM Backups\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e1785-ME16, 1785-ME32, 1785-ME64\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eOperating Temperature\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e0 to 60 degrees C (32 to 140 degrees F)\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003ePhysical Dimensions\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e237.5 x 183 x 55 mm\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003e\u003cspan\u003e\u003cstrong\u003eNet Hardware Weight\u003c\/strong\u003e\u003c\/span\u003e\u003c\/td\u003e\n\u003ctd\u003e\u003cspan\u003e1.45 kg (3.19 lbs)\u003c\/span\u003e\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003ch3\u003eEngineering Advantages\u003c\/h3\u003e\n\u003cul class=\"list-paddingleft-2\"\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eDeterministic Distributed Networking:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eDedicated onboard DH+ and Universal Remote I\/O (RIO) channels maintain highly stable update times for critical devices. At a baud rate of 230.4 kbps, the switch scans an entire 1771 rack subsystem in just 3 milliseconds, minimizing input propagation delays across extensive field wire runs.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eNon-Interrupted Memory Preservation:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eThe internal battery-backed SRAM structure retains essential machine operating profiles and bit registers through major electrical failures. To provide permanent defense against code wipeouts during extended storage, the board accepts plug-in 1785-ME series EEPROM memory cartridges.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eDirect Mechanical Keying Protection:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eThe module features a physical key-switch on the front faceplate. This switch locks the memory execution registers into \"Run Mode,\" preventing unauthorized remote software modifications, accidental network overrides, or unauthorized operator code changes.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eDual Controller Redundancy Capabilities:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eThe hardware architecture fully supports processor redundancy loops. Linking a secondary tracking unit ensures that control shifts smoothly to the standby processor if a primary CPU hardware fault triggers an interlock, eliminating unplanned facility line halts.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eHigh-Amp Backplane Drive:\u003c\/strong\u003e\u003cspan\u003e \u003c\/span\u003eThe module bus handles 2.5 Amps at 5V DC power directly from the 1771 chassis power supply module. This powerful energy distribution allows the processor to drive local, low-latency intelligent communication modules inside adjacent rack slots.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e\n\u003ch3\u003eFAQs\u003c\/h3\u003e\n\u003cul class=\"list-paddingleft-2\"\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eWhat critical precaution must maintenance teams observe when replacing the backup battery on the 1785-LT2?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eYou must perform the 1770-XYC lithium battery replacement while the control cabinet power remains turned ON. If you extract the old battery while the 1771 chassis is unpowered, the internal volatile SRAM registers lose their electrical bias instantly, deleting your entire automation program and configuration tag database.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eCan the 1785-LT2 operate within any standard 1771 expansion chassis?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eNo. The 1785-LT2 processor module must always slide into the designated, left-most master slot of a primary 1771 I\/O chassis (such as a 1771-A1B or 1771-A4B). The specialized pins in this specific slot link the processor directly to the backplane communication pathways to enable scanner traffic management.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003cli\u003e\n\u003cp\u003e\u003cstrong\u003eHow does the hardware handle memory expansion beyond the stock 13 Kwords?\u003c\/strong\u003e\u003c\/p\u003e\n\u003cp\u003eThe faceplate contains a dedicated expansion port that accepts plug-in memory cartridge sub-boards, including the 1785-ME16, 1785-ME32, or 1785-ME64. These accessories expand the total active workspace up to 17 or 21 Kwords to accommodate large math routines or extended recipes.\u003c\/p\u003e\n\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"Allen Bradley","offers":[{"title":"Default Title","offer_id":43387116355674,"sku":"1785-LT2","price":99.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0710\/5957\/0778\/files\/55_717072ea-9760-46aa-bb6f-97d1d94b58fb.jpg?v=1779070934","url":"https:\/\/www.spareoil.com\/products\/ab-1785-lt2-programmable-logic-controller-dh-rio-cpu","provider":"SpareOil Automation","version":"1.0","type":"link"}