Datasheet

dsPIC30F4011/4012

14.7 QEI Module Operation During CPU

Idle Mode

Since the QEI module can function as a quadrature

encoder interface, or as a 16-bit timer, the following

section describes operation of the module in both

modes.

14.7.1 QEI OPERATION DURING CPU IDLE

MODE

When the CPU is placed in the Idle mode, the QEI mod-

ule will operate if the QEISIDL bit (QEICON<13>) = 0.

This bit defaults to a logic ‘0’ upon executing POR and

BOR. For halting the QEI module during the CPU Idle

mode, QEISIDL should be set to ‘1’.

14.7.2 TIMER OPERATION DURING CPU

IDLE MODE

When the CPU is placed in the Idle mode and the QEI

module is configured in the 16-bit Timer mode, the

16-bit timer will operate if the QEISIDL bit (QEI-

CON<13>) = 0. This bit defaults to a logic ‘0’ upon

executing POR and BOR. For halting the timer module

during the CPU Idle mode, QEISIDL should be set

to ‘1’.

If the QEISIDL bit is cleared, the timer will function

normally as if the CPU Idle mode had not been

entered.

14.8 Quadrature Encoder Interface

Interrupts

The quadrature encoder interface has the ability to

generate an interrupt on occurrence of the following

events:

• Interrupt on 16-bit up/down position counter

rollover/underflow

• Detection of qualified index pulse or if CNTERR

bit is set

• Timer period match event (overflow/underflow)

• Gate accumulation event

The QEI Interrupt Flag bit, QEIIF, is asserted upon

occurrence of any of the above events. The QEIIF bit

must be cleared in software. QEIIF is located in the

IFS2 register.

Enabling an interrupt is accomplished via the respec-

tive Enable bit, QEIIE. The QEIIE bit is located in the

IEC2 register.