Power Management; Usb (Snapi, Usb Hid Keyboard, Etc.) - Motorola PL3307 Integration Manual

Power Management

The PL3307 has various power management options depending on the host interface.

USB (SNAPI, USB HID Keyboard, etc.)

The PL3307 automatically manages its power usage, including USB suspend mode. Additionally, when
drawing power from the USB bus, the PL3307 and imager engine do not exceed the USB limit of 500 mA (see
Interfaces on page
NOTE The PL3307 does not use Low Power mode when connected to a USB-based host.
SSI or RS-232
When using SSI or any RS-232 host interface, set the PL3307 to use one of the following power modes:
•
Continuous Power : The PL3307 is fully awake and running, even when not in a decode session.
•
Low Power (default): The PL3307 draws less current at idle than when in Continuous Power mode, and
is more suitable for battery-powered applications. See
Methods of Placing the PL3307 into Low Power Mode
Table 1-1
Set the Power Mode parameter to Low Power
(see Power Mode (Serial Hosts Only) on page
4-17)
Send the SLEEP command
(see Table 7-1 on page
Note: All Wake Up signals (see Table 1-2) must be inactive to enter Low Power mode.
In Low Power mode the PL3307 reduces its current draw whenever possible, and must be awakened before
performing any functions. Any of the following conditions wake the device.
Waking Up the PL3307
Table 1-2
Signal
HOST_AIM_WAKE*
HOST_TRIGGER*
HOST_CTS
When the PL3307 is awakened, it remains awake for 1 second (or for another value set via the
Low Power Mode on page
1-4).
Action
7-2)
State to Wake Up
Low
Low
Low
4-17) before re-entering Low Power mode.
Technical Specifications on page
Behavior
The PL3307 enters Low Power mode automatically
whenever possible.
The PL3307 enters Low Power mode only once, as
soon as possible.
Comment
Applies to SSI host only.
Getting Started 1 - 3
2-13.
Time Delay to