Siemens 6ES5255-1AA11 MONA Video Module

Technical Specifications and Video Processing

This MONA video module provides text and graphics display for Siemens SIMATIC S5 systems. The Siemens 6ES5255-1AA11 generates video signals for industrial monitors without additional hardware. You can install this unit into any standard S5-115U or S5-135U rack slot. Its dedicated video processor creates screens independently from the CPU scan cycle. The module weighs approximately 0.52 kilograms. Its dimensions measure 25 cm in height, 5 cm in width, and 21 cm in depth.

Parameter	Specification
Brand	Siemens
Model	6ES5255-1AA11
Category	MONA Video Module / Display Generator Unit
Weight	0.52 kg
Height	25 cm
Width	5 cm (single slot)
Depth	21 cm
Video Output Type	Composite video (BNC connector)
Video Standard	PAL or CCIR (selectable via jumper)
Display Resolution	64 characters x 16 lines (text mode)
Character Set	128 alphanumeric plus special symbols
Character Matrix	8 x 8 pixels per character
Graphics Resolution	512 x 256 pixels (bitmap mode)
Memory Capacity	8 KB video RAM + 4 KB character RAM
Number of Display Pages	2 pages (switchable)
Interface to CPU	16-bit parallel bus
Energy Storage	None (no battery)
Component Count	Video processor, RAM chips, oscillator, BNC driver

Display Modes and Screen Generation

The module operates in both text and graphics display modes independently. You can mix text overlays with graphic backgrounds on the same screen. The Siemens 6ES5255-1AA11 stores character definitions in onboard RAM. You can create custom symbols for machine-specific display needs. A hardware cursor indicates the current text entry position clearly. The module refreshes the display 50 times per second (PAL mode). Consequently, the image remains flicker-free and stable on any monitor. Two display pages allow rapid screen switching without reloading data.

MONA Protocol and CPU Communication

The module follows the MONA (Monitor Adapter) communication protocol standard. This protocol defines data exchange between the S5 CPU and video hardware. The Siemens 6ES5255-1AA11 appears as an I/O module in the S5 address space. You control all display functions through simple memory writes. The CPU updates screen data without any special video programming knowledge. An 8-position DIP switch sets the module’s base address. The module acknowledges each data transfer with a status flag.

Installation and Video Connection Guidelines

You must insert this module into any standard S5 I/O rack slot. The backplane supplies 5V DC power to the video circuits. The Siemens 6ES5255-1AA11 uses a BNC connector on the front panel for video output. You must use 75-ohm coaxial cable to connect to an industrial monitor. This cable prevents signal reflections and image ghosting problems. The module draws approximately 300 mA from the 5V supply rail. You should terminate the video cable at the monitor end only. A front-panel LED indicates valid video signal generation.