Wake Up Timing - Honeywell IS4910 Integration Manual

Wake Up Timing

When exiting sleep mode the engine will require a minimum wake up time before an image can be acquired.
Wake up is initiated by pulsing the Illum_On pin for a minimum of 250 µS. The pulsing wakes up the on board
microcontroller and oscillator. After this pulse is brought low, an additional 10 mS delay is required to ensure
that the oscillator has stabilized. After the additional 10 mS delay, the oscillator is stabilized and the imager is
ready to receive its configuration via the I
During sleep, the imager looses all configuration settings therefore all applicable settings will need to be
updated. The total time for the device to wake up will be dependant on how many registers need to be
reconfigured, the running speed of the I
(i.e. repeated stop vs. no repeat stop transmission).
Wake up time calculation:
T = Oscillator Stabilization Time + Illum_On pulse width + Configuration Time
wake up
= 10 mS + 250 µS + Configuration Time
= 10.25 mS + Configuration Time
Example: The following waveform illustrates the wake up time measured from the rising edge of the Illum_On
signal to the last byte of configuration data sent on the I
below is for a host system running the I
In this example, 27 registers are configured. The total wake up time under the example conditions
is approximately 31.5 mS.
18
2
C control bus.
2
C bus, and the manner in which the data is transmitted on the bus
Figure 13. Example of wake up timing with I
2
C bus (labeled as SCL). The example
2
C at 100kHz and transmitting data using no repeat stop.
2
C running at 100 kHz