Metrologic Instruments IS4921 - Manual (Page 22)

16
Theory of Operation
Overview
The IS4920 decode imaging engine series is ideal for integration into data terminals and other small devices.
The high-quality images produced by the imaging engine can be used for decoding bar codes, image upload,
signature capture, document lifting and reading OCR fonts.
The decode engine consists of two main system components: the a non-decode imaging engine, which utilizes
a high-resolution CMOS image sensor, and a small decode board that contains a powerful microprocessor and
the firmware to control all aspects of the engine’s operations and enabling communication with the host system
over the standard set of communication interfaces.
The model IS492x-xx103 provides communication with the host system over TTL-level RS232 communication
interface.
The model IS492x-xx38 provides communication with the host system over USB. It can be configured for the
following protocols of USB communication:
• USB Keyboard Emulation Mode (default)
• USB Serial Emulation Mode
The system hardware architecture of the decode engine is shown in the figure below.
Figure 16. IS4920 / IS4921 System Architecture