Microprocessors 2 lesson 7

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Microprocessors 2lesson 7
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Subjects lesson 7

• Planning
• Interrupts
• Serial communication /USART
• Questions

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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

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Interrupt Logic
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Program memory map
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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)
varvar2 if (vargt255) var1
T0IF 0 / reset flag /
int_restore_registers // W, STATUS (and
PCLATH)
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Main program interrupts
void main( void) while (1)

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Serial CommunicationIntoduction

• Morse code telegraphy
• 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

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RS232-C 1
Serial Communication

• 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))

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RS232DB9-connector
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RS232SynchroneA-Synchrone
Serial Communication

• 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)

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RS232Voltages
Serial Communication

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Cabellenght versus baudrate
Serial Communication

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Serial communication PIC16F688
Asynchronous - Auto-wake-up - Auto baud
calibration - 13-bit Break character
Synchronous selectable clock Synchronous
clock polarity
Serial Communication
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Transmit statuscontrol register
bit 7 CSRC Clock Source Select bit Asynchronous
mode Dont care Synchronous mode 1 Master
mode (clock generated internally from BRG) 0
Slave mode (clock from external source) bit 6
TX9 9-bit Transmit Enable bit 1 Selects 9-bit
transmission 0 Selects 8-bit transmission bit 5
TXEN Transmit Enable bit 1 Transmit enabled 0
Transmit disabled Note SREN/CREN overrides
TXEN in Sync mode. bit 4 SYNC USART Mode Select
bit 1 Synchronous mode 0 Asynchronous
mode bit 3 SENDB 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 Dont care bit 2
BRGH High Baud Rate Select bit Asynchronous
mode 1 High speed 0 Low speed Synchronous
mode Unused in this mode bit 1 TRMT 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.
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Buad ratecontrol
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Baud ratecalculating
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SETUPfor serialcommunication
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Exercise
Serial Communication

• 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