Simple Serial Interface (Ssi); Power Management - Symbol SE955 Integration Manual

1-4 SE955 Integration Guide

Simple Serial Interface (SSI)

The SE955 scan engine is host controlled through the Simple Serial Interface (see
of operation (see Triggering Modes on page
• Scan mode
• Aim mode which provides a laser aim dot
• Blink mode for presentation scanning
• Continuous mode.
In Scan mode the pre-selected scan amplitude is used. I.e., 35° and 47° (default). Also see,
page 8-11.
The Aim mode is used to provide a laser aim dot, which can be used to pre-align the scan engine to a bar code before scanning. To
aim then scan, the host would control the engine using the hardware AIM/WKUP* then TRIG* lines at the SSI interface (see
3), or by SSI commands (see Chapter 10, Simple Serial
The Blink mode can be used for triggerless operation in presentation scanning applications. To minimize power consumption, low duty
cycle scanning is performed until a change in background is detected. Once detected, high duty cycle scanning is performed until the
bar code, if one is present, is decoded. The scan engine would then return to low duty cycle scanning until the next change in
background is detected (see Triggering Modes on page
The Continuous Scanning mode is the mode in which the scan engine is always scanning and decoding (see
12).

Power Management

The SE955 has two power states (Awake and Sleep) and two power modes (Continuous Power and Low Power).
Power States
WAKEUP and SLEEP commands (see
state to Awake or Sleep. The Low Power mode has an automatic timer that puts the unit into the Sleep state after a specified period
of time.
When the SE955 is in the Sleep power state the PWRDWN signal (see
power from the SE955. Do not remove power without using this signal since the PWRDWN signal is the only indication if the decoder
is not transmitting, receiving, decoding, or writing data to non-volatile memory.
Power Modes
Power modes are controlled by the Power Mode parameter (see
• In Continuous Power mode, the scan engine remains in the Awake state after each decode attempt. The Continuous
Power mode parameter (see
receives a SLEEP command. In this mode, the SE955 can switch power states using the SLEEP and WAKEUP commands (see
SLEEP on page 10-22
• In Low Power mode, the scan engine enters into a low power consumption Sleep state whenever possible (provided all
WAKEUP commands were released), drawing less current than in Continuous Power mode. This makes the Low Power mode
more suitable for battery powered applications. The Low Power mode also allows the SE955 to switch power states using
the SLEEP and WAKEUP commands (see
from the Sleep power state before performing any functions.
8-13), including:
Interface).
8-13).
WAKEUP on page 10-25
Power Mode on page 8-12) sets the SE955 to remain in the Awake power state unless it
and WAKEUP on page 10-25); automatic power state switching is not supported.
SLEEP on page 10-22
Table 1-3), and supports various triggering modes
and SLEEP on page 10-22), are sent to the scan engine to set the Power
Table 1-3) is asserted. The host uses this signal to remove
Power Mode on page 8-12).
and WAKEUP on page
Scan Angle on
Power Mode on page 8-
10-25). The SE955 must be awakened
Table 1-