Acromag PMC521 422/485 Octal Serial Communication Module

The Acromag PMC521 is an octal serial communication module for PCI Mezzanine Card slots, delivering eight independent channels of RS-422B/EIA-485 serial communication in a single-width form factor. Each channel operates full-duplex with 64-byte FIFO buffers on both transmit and receive paths, minimizing CPU overhead and interrupt loads in high-density serial connectivity applications. The module supports programmable baud rates to 1.8432 Mbps (standard crystal) and up to 20 Mbps maximum, with software-configurable character formats (5–8 bits), stop bits (1, 1.5, or 2), and parity (odd, even, or none).

Integrated line-break detection, failsafe receivers, and comprehensive error detection protect signal integrity in demanding industrial environments. A global interrupt source register across all eight channels simplifies multi-port monitoring and control.

Technical Specifications

• Eight asynchronous full-duplex RS-422B serial ports with EIA-485 compatibility


• Maximum data rate: 20 Mbps; programmable baud rate to 1.8432 Mbps (standard crystal)


• 64-byte transmit and receive FIFO buffers per channel


• Character size: 5–8 bits (software-programmable)


• Stop bits: 1, 1.5, or 2 (software-programmable)


• Parity: Odd, even, or none (software-programmable)


• Power supply: +5V ±5%; current draw consult factory


• Operating temperature: 0–70°C (PMC521-64) or −40–85°C (PMC521-64E)


• Storage temperature: −55–125°C


• MTBF: 2,321,047 hours @ 25°C per MIL-HDBK-217F notice 2


• 4 kB memory space; 32-bit PCI target (Altera FPGA implementation)

Key Features

• Independent non-isolated serial ports with common single return


• Per-channel interrupt control: transmit, receive, line status, data set, and flow control


• Selectable double-buffered or 64-byte FIFO data register buffering


• Line-break and false start-bit detection


• Failsafe receiver architecture


• Xon/Xoff and special character detection


• PCI Local Bus Specification Rev. 2.3 and CMC/PMC P1386.1 conformance


• 5V compliant, 3.3V tolerant signaling


• Socketed termination and bias resistors

Typical Applications Industrial automation, data acquisition systems, multi-port serial communication networks, and real-time control requiring high-density RS-422/485 connectivity with minimal latency.

Compatibility & Integration Available with front I/O connector (PMC521, PMC521E) or rear I/O connector (PMC521R, PMC521RE). Relative humidity: 5–95% non-condensing.