Since many host systems and applications have unique formats and protocol requirements, the decode engine supports a wide range of configurable features. These features may be selected by scanning a corresponding configuration bar code from the MetroSelect Single-Line Configuration Guide or Area Imaging Bar code Supplemental Configuration Guide. Both guides are available for download at www.honeywell.com/aidc under the IS4920 product page.

Usage of the Host Interface Signals

In the default “multi-try” trigger mode of operations, the scanning engine is activated by the nTrig signal, which must be kept active (low) until the successful scan is achieved, as indicated by the nGoodRead signal.

Upon a successful scan, the decode engine asserts the nGoodRead signal and keeps it asserted (low) for the duration of transmission of the decoded data to the host, or for the minimum of 100 msec (configurable to 50 msec), which coincides with the duration of the nBeeper signal.

The nGoodRead and nBeeper signals are driven with LVC family open drain outputs and are pulled up on the decode board with 100K resistors to VIN. The default state of these pins is Hi-Z (pulled up via 100K) and these signals are capable of sinking up to 24mA each when driven to the low state. For beeper applications, care must be taken to ensure that inductive spikes do not cause the voltage on the lines to exceed the maximum voltage of 5.5V.

Warning: The nGoodRead and nBeeper signals are not current limited. The external host circuitry connected to these pins must ensure that the current is limited to 25mA.

At any given time, the decode engine can be in one of the following power modes, see page 20 for descriptions:

•Boot Mode

•Operating Mode

•Idle Mode

•Sleep Mode

•Presentation Wakeup Mode

•Power-down Mode (TTL Only)

•Suspend Mode (USB Only)

When the decode engine is in the Sleep or Presentation Wakeup Mode, the nWake or nTrig signals can be used to wake up the engine.

The nWake signal wakes up the engine and turns the engine into the Idle Mode, which in the TTL RS232 version enables communication with the host for a short period of time defined by the value of the sleep timeout, which is set to one second by default.

Note: In the USB decode engines with USB Serial Emulation Mode activated; communication with the host is enabled even when the engine is in the Sleep or Presentation Wakeup Mode.

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