multiprocessor communications

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Multiprocessor communications

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Page 1: Multiprocessor communications

Multiprocessor communications

Page 2: Multiprocessor communications

Example 12.5

The master has been designated the address A whereas the slaves X,Y and Z have been designated the addresses B,C and D in hexadecimal. The master system wishes to send 50 bytes stored in memory to one of the slaves, say Z. Explain the sequence of operation.

Page 3: Multiprocessor communications

Master-slave configuration

Page 4: Multiprocessor communications

Mode 0

Page 5: Multiprocessor communications

Mode 1

Page 6: Multiprocessor communications

Mode 2 & Mode 3

Page 7: Multiprocessor communications

Sequence of operation

BAUD_RATE needs to be decided

BAUD_RATE register will be loaded

Page 8: Multiprocessor communications

Baud RateSource :XTAL1 frequency

MSB=1

B=BAUD_RATE register contents(15bits)+1

Mode 0:

BAUD RATE = XTAL1 frequency/(4*B)

Other Modes :

BAUD RATE = XTAL1 frequency/(64*B)

Page 9: Multiprocessor communications

I/0 Control Register

Page 10: Multiprocessor communications

Serial port control

Page 11: Multiprocessor communications

Mode 2

Master system:

TB8 =1 ,REN=1, PEN=0, M2 M1=10

i.e. SP_CON =00011010=1AH

Slave register:

TB8 =0 ,REN=1, PEN=0, M2 M1=10

i.e. SP_CON =00001010=0AH

Page 12: Multiprocessor communications

Enabling SIO

• SIO must be enabled in the masters as well as the slaves by making Interrupt mask register bit 6 = 1

i. e. IMR=01000000B=40H

Page 13: Multiprocessor communications

Address frame

Start Sender address

Receiver address

TB8 Stop

1 1010 1101 1 1

Page 14: Multiprocessor communications

SIO SR (slave systems)

Read SP_STAT

Branch to RI_ISR

Compare receiver address with system address

If not equal then enable interrupt

Return

Else switch to mode 3 by modifying SP_CON

Page 15: Multiprocessor communications

Mode 3

Slave register:

TB8 =0 ,REN=1, PEN=0, M2 M1=11

i.e. SP_CON =00001011=0BH

(modified SP_CON for slave)

Page 16: Multiprocessor communications

Mode 3

(Master modifies SP_CON to make 9th bit=0)

TB8 =0 ,REN=0, PEN=0, M2 M1=11

i.e. SP_CON =00000011=03H

Note:

M2M1=10 will also work

Page 17: Multiprocessor communications

SIO ISR(Master system)

Read SP_STAT

Branch to RI_ISR

TI ISR in master

load the next byte in SBUF(TX)

Enable interrupt

Return

Page 18: Multiprocessor communications

SIO ISR(Slave system)

Read SP_STAT

Branch to RI_ISR

RI ISR in slave Z

Read the data byte

Check if it is the last byte

If yes then enable interrupt

Return

Else store the data byte

Enable interrupt

Return

Page 19: Multiprocessor communications

THANK YOU