Specifications

25
THEORY OF OPERATION
Descriptions of IS4920 Power Modes
Boot Mode
The scanner is booting up.
PWRDWN Pin State: Asserted (HIGH).
Transition to Boot Mode:
• The IS4920-xx103 TTL RS232 scanner is turned to Boot Mode from
Power-down Mode when the power is applied AND upon reception of
the nTrig or nWake signals.
• The IS4920-xx38 USB enters Boot Mode upon completion of USB
enumeration.
• The scanner can turn itself to Boot Mode from Operating or Idle mode
upon some internal event, such as at the end of the software upgrade
procedure.
At the end of the boot-up cycle the scanner turns to the Idle Mode and de-asserts
the PWRDWN pin.
Operating Mode
The scanner is acquiring and processing images or running other tasks.
PWRDWN Pin State: De-asserted (LOW).
Transition to Operating Mode:
• The scanner is turned to Operating Mode from Idle, Sleep, or
Presentation Wakeup Modes upon the reception of the nTrig signal.
• The scanner can be turned to Operating Mode from Idle Mode (or Sleep
Mode) upon the reception of a special single-byte serial command from
the host. The byte value is configurable.
• The scanner is turned to Operating Mode from the Presentation
Wakeup Mode upon the object detection event.