DSPIC33FJ256MC710-I/PT Microchip Technology, DSPIC33FJ256MC710-I/PT Datasheet - Page 23

• Manufacturer Part Number: DSPIC33FJ256MC710-I/PT
• Description: IC DSPIC MCU/DSP 256K 100TQFP
• Manufacturer: Microchip Technology
• Series: dsPIC™ 33Fr

Specifications of DSPIC33FJ256MC710-I/PT

• Program Memory Type: FLASH
• Program Memory Size: 256KB (256K x 8)
• Package / Case: 100-TFQFP
• Core Processor: dsPIC
• Core Size: 16-Bit
• Speed: 40 MIPs
• Connectivity: CAN, I²C, IrDA, LIN, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, DMA, Motor Control PWM, QEI, POR, PWM, WDT
• Number Of I /o: 85
• Ram Size: 30K x 8
• Voltage - Supply (vcc/vdd): 3 V ~ 3.6 V
• Data Converters: A/D 24x10b/12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Product: DSCs
• Data Bus Width: 16 bit
• Processor Series: DSPIC33F
• Core: dsPIC
• Maximum Clock Frequency: 40 MHz
• Number Of Programmable I/os: 85
• Data Ram Size: 30 KB
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• 3rd Party Development Tools: 52713-733, 52714-737, 53276-922, EWDSPIC
• Development Tools By Supplier: PG164130, DV164035, DV244005, DV164005, PG164120, DM240001, DM240002, DM330011, DM300019, DV164033, MA330011, MA330012, DM300024
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: 876-1001 - DSPIC33 BREAKOUT BOARDAC164333 - MODULE SKT FOR PM3 100QFPMA330013 - MODULE PLUG-IN DSPIC33 100TQFPDV164033 - KIT START EXPLORER 16 MPLAB ICD2DM240001 - BOARD DEMO PIC24/DSPIC33/PIC32
• Eeprom Size: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

62. Module: QEI
EXAMPLE 1:
© 2010 Microchip Technology Inc.
unsigned int POSCNT_b15 = 0;
unsigned int Motor_Position = 0;
int main(void)
{
}
void __attribute__((__interrupt__)) _QEIInterrupt(void)
{
}
The Quadrature Encoder Interface (QEI) module
does not generate an interrupt when MAXCNT is
set to 0xFFFF and the following events occur:
1. POSCNT underflows from 0x0000 to 0xFFFF
2. POSCNT stops
3. POSCNT overflows from 0xFFFF to 0x0000
This sequence of events occurs when the motor is
running in one direction, which causes POSCNT to
underflow to 0xFFFF. Then, if the motor stops and
starts running in the opposite direction, an
overflow from 0xFFFF to 0x0000 will be
generated. The QEI module does not generate an
interrupt when this condition occurs.
// ... User's code
MAXCNT = 0x7FFF;
Motor_Position = POSCNT_b15 + POSCNT;
// ... User's code
IFSxbits.QEIIF = 0;
POSCNT_b15 ^= 0x8000; // Overflow or Underflow
// Instead of 0xFFFF
// Clear QEI interrupt flag
// x=2 for dsPIC30F
// x=3 for dsPIC33F
Work around
To prevent this condition from occurring, set
MAXCNT to 0x7FFF, which will cause an interrupt
to be generated by the QEI module.
In addition, a global variable could be used to keep
track of bit 15, so that when an overflow or
underflow condition is present on POSCNT, the
variable will toggle bit 15. Example 1 shows the
code required for this global variable.
Affected Silicon Revisions
A2
X
A3
X
A4
X
DS80447D-page 23