ScanTool STN11xx - Manual (Page 3)

STN11xx PowerSave
1.0 PowerSave Functionality
STN11xx features a sophisticated power manage-
ment system (PowerSave™) that can be used to put
the device in low power mode. The primary purpose of
PowerSave is to prevent the vehicle’s battery from
being drained when the device is left plugged in for
extended periods of time (e.g., permanent in-vehicle
installations).
The concept of a trigger is key to understanding
the operation of PowerSave. A trigger is an event or a
condition that causes the device to either go to sleep,
or wake up from sleep. “Go to sleep after 5 minutes of
UART inactivity” and “wake up when vehicle system
voltage goes above 12.8 volts” are examples of
triggers. Each trigger can be independently enabled or
disabled.
The following sections describe the PowerSave
functionality, while section 2.0 describes the
commands and parameters used to configure and
control the power management system. You can use
the STSLCS command to print a summary of the active
PowerSave configuration settings.
1.1 Control Modes
There are two control modes for the PowerSave
functionality: native and ELM327. Use bit 7 (“master
enable”) of the programmable parameter 0E (PP 0E) to
switch between the modes. See the description of the
AT PP command for more information about PP 0E.
By default, STN11xx is operating in the native
PowerSave control mode.
1.1.1 Native PowerSave Mode
When the “master enable” bit of PP 0E is cleared,
or PP 0E is off, STN11xx is in the native PowerSave
control mode.
In this mode, the rest of the 0E programmable
parameter bits are ignored and the PowerSave is
controlled exclusively via STSL commands. In native
mode, the ATLP command is unavailable. Also, the
ELM327 “ACT ALERT” and “LP ALERT” messages are
not displayed.
1.1.2 ELM327 Low Power Mode
Note: this mode had been implemented for
compatibility with software written for the ELM327. The
native PowerSave mode has a number of important
advantages over the ELM327 Low Power mode,
including greater flexibility, more straightforward
configuration, and default settings that had been
optimized for more reliable performance.
When the “master enable” bit of the 0E
programmable parameter is set and PP 0E is on,
STN11xx is in the ELM327 control mode.
In this mode, most PowerSave settings are
overridden by the PP 0E. However, the following
settings that do not have a PP 0E equivalent can still
be adjusted via their corresponding STSL commands:
• UART wakeup pulse timing (SLUWP)
• External SLEEP input polarity (SLXP)
• Voltage based triggers (SLVL, SLVLS,
SLVLW, SLVG, SLVGW)
By default, instead of the fixed ELM327 minimum
UART Rx wakeup pulse requirement of 128 μs,
STN11xx pulse width is set to 0 (20 ns). This is done
to allow the user to wake up the device by sending
characters, even at highest supported UART baud
rate.
In the ELM327 PowerSave control mode, STSLCS
command will report the actual active configuration that
is set via the 0E programmable parameter.
STN11xx external SLEEP input functions as the
ELM327 IgnMon input.
1.2 Sleep Triggers
Device can be put to sleep using one of the four
sleep triggers:
• Sleep commands (STSLEEP and ATLP)
• UART inactivity (SLU)
• External SLEEP input (SLX)
• Voltage level (SLVL)
Multiple sleep triggers can be enabled at the same
time. The first trigger that gets activated will put the
device to sleep.
By default, all sleep triggers are off.
Warning: before you enable a sleep trigger or issue
the STSLEEP command, make sure that the wakeup
triggers are enabled and properly configured. The only
other means of bringing the device out of the sleep
state is to initiate a hardware reset, either via the
RESET
¯¯¯¯¯ input, or by cycling the power.
1.2.1 STSLEEP and ATLP commands
The device will go to sleep when it receives the
ATLP or STSLEEP command. The ATLP command is
available only in the ELM327 Low Power Mode.
The STSLEEP command has an optional delay
parameter. The purpose of the delay is to prevent the
device from going to sleep prematurely: some hosts
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