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Microprocessors 2 lesson 7

Microprocessors 2 lesson 7. Subjects lesson 7. Planning Interrupts Serial communication /USART Questions. Interrupt sources. • External Interrupt RA2/INT • TMR0 Overflow Interrupt • PORTA Change Interrupts • 2 Comparator Interrupts • A/D Interrupt • Timer1 Overflow Interrupt

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Microprocessors 2 lesson 7

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  1. Microprocessors 2lesson 7

  2. Subjects lesson 7 • Planning • Interrupts • Serial communication /USART • Questions

  3. Interrupt sources • • External Interrupt RA2/INT • • TMR0 Overflow Interrupt • • PORTA Change Interrupts • • 2 Comparator Interrupts • • A/D Interrupt • • Timer1 Overflow Interrupt • • Timer2 Match Interrupt • • EEPROM Data Write Interrupt • • Fail-Safe Clock Monitor Interrupt • • Enhanced CCP Interrupt

  4. Interrupt Logic

  5. Program memory map

  6. Interrupt Software #include "int16CXX.H" #pragma origin 4 interrupt int_server( void) { int16 var; int_save_registers // W, STATUS (and PCLATH) if (T0IF) { /* TMR0 overflow interrupt */ TMR0 = -255; CharToLed(var); var=var*2; if (var>=255) var=1; T0IF = 0; /* reset flag */ int_restore_registers // W, STATUS (and PCLATH) }

  7. Mainprogram interrupts void main( void) { while (1) { } }

  8. Serial CommunicationIntoduction • Morse codetelegraphy • RS-232 (low-speed, implemented by Serial Ports) • RS485 • Universal Serial Bus (moderate-speed, for connecting computers to peripherals) • FireWire • Fibre Channel (high-speed, for connecting computers to mass storage devices) • InfiniBand (very high speed, broadly comparable in scope to PCI) • Serial Attached SCSI • Serial ATA • PCI Express

  9. Serial Communication RS232-C 1 • Half duplex • Full duplex • 5,6,7,8 databits • ASCII (0-127) • Stop bit(s) • Parity • DCE (Data communication equipment) • DTE(Data terminal Equipment (PC))

  10. 9 Pin Connector on a DTE device (PC connection) Male RS232 DB9 Pin Number Direction of signal: 1 Carrier Detect (CD) (from DCE) Incoming signal from a modem 2 Received Data (RD) Incoming Data from a DCE 3 Transmitted Data (TD) Outgoing Data to a DCE 4 Data Terminal Ready (DTR) Outgoing handshaking signal 5 Signal Ground Common reference voltage 6 Data Set Ready (DSR) Incoming handshaking signal 7 Request To Send (RTS) Outgoing flow control signal 8 Clear To Send (CTS) Incoming flow control signal 9 Ring Indicator (RI) (from DCE) Incoming signal from a modem RS232DB9-connector

  11. Serial Communication RS232SynchroneA-Synchrone • Synchrone: • Always dataflow of bits to synchronisize • A-Synchrone; • When no data needed to send no dataflow. Synchronysation by start and stop bits (So slower)

  12. RS232 Level Transmitter (V) Receiver (V) Space status (0) +5 ... +15 +3 ... +25 Mark status (1) -5 ... -15 -3 ... -25 Not defined - -3 .. -3 …+3 . +3 Serial Communication RS232Voltages

  13. RS232 kabellengte volgens Texas Instruments Baud rate Maximum cabellength(m) 19200 15 9600 150 4800 300 2400 900 Serial Communication Cabellenght versus baudrate

  14. • Asynchronous - Auto-wake-up - Auto baud calibration - 13-bit Break character • Synchronous – selectable clock • Synchronous – clock polarity Serial Communication Serial communication PIC16F688

  15. bit 7CSRC: Clock Source Select bit Asynchronous mode: Don’t care Synchronous mode: 1 = Master mode (clock generated internally from BRG) 0 = Slave mode (clock from external source) bit 6TX9: 9-bit Transmit Enable bit 1 = Selects 9-bit transmission 0 = Selects 8-bit transmission bit 5TXEN: Transmit Enable bit 1 = Transmit enabled 0 = Transmit disabled Note: SREN/CREN overrides TXEN in Sync mode. bit 4SYNC: USART Mode Select bit 1 = Synchronous mode 0 = Asynchronous mode bit 3SENDB: Send Break Character bit Asynchronous mode: 1 = Send Sync Break on next transmission (cleared by hardware upon completion) 0 = Sync Break transmission completed Synchronous mode: Don’t care bit 2BRGH: High Baud Rate Select bit Asynchronous mode: 1 = High speed 0 = Low speed Synchronous mode: Unused in this mode bit 1TRMT: Transmit Shift Register Status bit 1 = TSR empty 0 = TSR full bit 0 TX9D: 9th bit of Transmit Data Can be address/data bit or a parity bit. Transmit status+control register

  16. Buad ratecontrol

  17. Baud ratecalculating

  18. SETUPfor serialcommunication

  19. Serial Communication Exercise • In the last week of this quarter you have to finish a programm what shows the working of the serial port. You can do this with 2 persons. • The programm on the 2 boards has to send the measured value from AN0 analogue input to the other board. The value received from the other board has to be shown , binary, on the 8 leds

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