Keysight / Agilent / HP E2261A Quad RS-232 Interface M-Module

The Keysight E2261A is a single-wide, register-based M-Module that delivers four independent RS-232 serial communication channels for embedded and industrial systems. This dense double-sided design integrates into M-Module carriers, providing full-duplex asynchronous DTE ports with programmable baud rates, data formatting, and both software and hardware handshaking. Each channel operates independently with dedicated 2 KB input and output buffers, enabling reliable serial device control and data acquisition across distributed test systems.

## Technical Specifications

• **Channels:** 4 independent RS-232 serial ports (full-duplex, asynchronous DTE)
• **Baud Rates:** 13 fixed rates from 75 baud to 38,400 baud
• **Data Length:** 5, 6, 7, or 8 bits (independently programmable per channel)
• **Parity:** None, Odd, Even, Always 1, or Always 0 (independently programmable)
• **Stop Bits:** 1, 1.5, or 2 bits (independently programmable)
• **Buffering:** 2 KB per channel (input and output)
• **Distance Rating:** Up to 50 feet
• **Isolation:** None

## Key Features

• Hardware handshaking: DTR/DSR (initial pacing) and RTS/CTS (transfer pacing)
• Software handshaking: Xon/Xoff flow control
• Conforms to ANSI/VITA Std 12-1996 for single-wide M-Modules
• Each module addressable within carrier for flexible multi-module configurations
• Option 001 breakout cable routes all four interfaces to separate locations

## Compatibility & Integration

Recommended for the E2251A C-size M-Module carrier. Compatible with E2250A carriers. Operates in VXI, Ethernet, and LXI systems. Use in PCI, cPCI, VME, or PXI carriers may require an adjacent slot to remain open. VXIPlug&Play drivers were available.