Microchip Technology dsPIC30F - QEI Operation During Power Saving Modes; Effects of a Reset

© 2004 Microchip Technology Inc. DS70063C-page 16-19
Section 16. Quadrature Encoder Interface (QEI)
Quadrature Encoder
Interface (QEI)
16
16.9 QEI Operation During Power Saving Modes
16.9.1 When the Device Enters Sleep
When the device enters Sleep mode, the QEI will cease all operations. POSCNT will stop at the
current value. The QEI will not respond to active signals on the QEA, QEB, INDX or UPDN pins.
The QEICON register will remain unchanged.
If the QEI is configured as a timer/counter, QEIM<2:0> = ‘001’, and the clock is provided
externally, TQCS = 1, the module will also cease operation during Sleep mode.
When the module wakes up, the quadrature decoder will accept the next transition on the QEA
or QEB signals and compare that transition to the last transition before Sleep to determine the
next action.
16.9.2 When the Device Enters Idle
The module will enter a power saving state in Idle mode depending on the QEISIDL bit
(QEICON<13>).
If QEICSIDL = 1, then the module will enter the power saving mode, similar to actions while
entering Sleep mode.
If QEICSIDL = 0, then the module will not enter a power saving mode. The module will continue
to operate normally while the device is in Idle mode.
16.10 Effects of a Reset
Reset forces module registers to their initial reset state. See Register 16-1 for all initialization
and reset conditions for QEI module related registers.
The quadrature decoder and the POSCNT counter are reset to an initial state.