Product Description:

The HCMCIF-0 is a communication interface module produced by B & R Automation for the HCM Maestro PLC Modules series. Installed beside the primary controller, this module establishes a dedicated serial link that allows the Maestro platform to exchange process data with coprocessors and auxiliary hardware in real-time automation tasks. By adding an independent channel for data blocks, message acknowledgments, and diagnostic codes, it extends the local PLC’s ability to coordinate multiple motion or I/O resources without burdening the main CPU scan time.

The interface maintains a buffer overhead of 32 bytes, reserving fixed memory space so incoming packets can be validated before host access. During serial reception, the Coma transfer path executes at 10 µs/byte, while the complementary Comc path completes at 15 µs/byte; these values quantify byte-level latency for the two internal DMA engines. Application code can enable the coprocessor data mode called Coordinated Except G-Addresses, which synchronizes user variables while leaving G-area tables under separate control. For direct reads and writes, the descriptor tag plc1 is used so the firmware can point transactions to the correct symbol list without additional mapping. Communication occurs over a Serial interface, and each completed block experiences 150 µs of transfer overhead before it is released to the task scheduler.

All G-addresses are stored in Dual Port RAM, allowing the module and the MCO1/2 host controller to access the same data word in a single cycle. Each transfer must span at least 500 locations, a limit that helps keep bus turnaround times predictable when only the local PLC CPU is the direct access target. Hardware allocation is simple because the carrier requires a minimum of two MCO slots, and no Sponet bus is needed when the module operates in its uncoordinated fallback mode.