DSPIC30F3011-30I/PT Microchip Technology, DSPIC30F3011-30I/PT Datasheet - Page 10

• Manufacturer Part Number: DSPIC30F3011-30I/PT
• Description: IC DSPIC MCU/DSP 24K 44TQFP
• Manufacturer: Microchip Technology
• Series: dsPIC™ 30Fr

Specifications of DSPIC30F3011-30I/PT

• Program Memory Type: FLASH
• Program Memory Size: 24KB (8K x 24)
• Package / Case: 44-TQFP, 44-VQFP
• Core Processor: dsPIC
• Core Size: 16-Bit
• Speed: 30 MIPs
• Connectivity: I²C, SPI, UART/USART
• Peripherals: Brown-out Detect/Reset, Motor Control PWM, QEI, POR, PWM, WDT
• Number Of I /o: 30
• Eeprom Size: 1K x 8
• Ram Size: 1K x 8
• Voltage - Supply (vcc/vdd): 2.5 V ~ 5.5 V
• Data Converters: A/D 9x10b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Product: DSCs
• Data Bus Width: 16 bit
• Processor Series: DSPIC30F
• Core: dsPIC
• Maximum Clock Frequency: 30 MHz
• Data Ram Size: 1024 B
• 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, ICE4000, DM240002, DM330011, DM300018
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With: XLT80PT3 - SOCKET TRAN ICE 80MQFP/TQFPAC30F006 - MODULE SKT FOR DSPIC30F 44TQFPAC164305 - MODULE SKT FOR PM3 44TQFPDV164005 - KIT ICD2 SIMPLE SUIT W/USB CABLE
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: DSPIC30F301130IPT

dsPIC30F3010/3011
16. Module: QEI Interrupt Generation
EXAMPLE 8:
DS80389B-page 10
unsigned int POSCNT_b15 = 0;
unsigned int Motor_Position = 0;
int main(void)
{
}
void __attribute__((__interrupt__)) _QEIInterrupt(void)
{
}
The 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. Once this happens, the
motor stops and starts to run in the opposite
direction, which generates an overflow from
0xFFFF to 0x0000. 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 8 shows the
code required for this global variable.
© 2008 Microchip Technology Inc.