EDUSAT SESSION FOR ADVANCED MICROPROCESSOR EC54

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EDUSAT SESSION FOR ADVANCED MICROPROCESSOR
(EC54) Date 08.11.2005 Session VII Topic
Programming Examples Faculty Anita Kanavalli
MSRIT
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Program 9

Write a program to compute factorial of a
positive number using recursive
procedure Program .MODEL SMALL .STACK
64H .DATA Num DW 04H Fact DW ?
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Program 9

.CODE MOV AX,_at_DATA MOV DS,AX MOV BX,Num CALL
FACT MOV AH,4CH INT 21H .EXIT
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Program 9

FACT PROC CMP BX,00H JE Next PUSH BX DEC BX CALL
FACT POP BX MUL BX
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Program 9

RET Next MOV AX,01H RET ENDP END
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Interfacing

• PPI or Multi Function Devices (MFD)

F0
D- BF
I/O
FN1
C P U
FN2
F1
I/O
System Bus
SW Register
F2
I/O
CW Register
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Interfacing

• D-Buf is the data buffer
• System Bus- carries ADDR,DATA,CONTROL
• FN1,FN2,FN3,F0,F1.. Are functional circuits
  (MFC)
• MFCs could be I/O ports, Timers, Transmitters,
  Receivers etc
• MFC- Independent function
• Each MFC has UNIQUE ADDRESS
• SW Register- Status register

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Interfacing

• SW register- could be absent as in 8255A
• CW register- must be present in all MFDs (
  PPIs)
• There could be more than one CW register
• Each SW and CW also has UNIQUE ADDRESS
• CW- defines (prepares) a functional unit in one
  of the modes
• SW- tells the status of various functional
  devices

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Interfacing

• PROGRAMMING ?
• SEND CONTROL WORD / WORDS
• SEND/RECEIVE DATA TO/FROM each functional unit

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Interfacing

• I/O s
• Logic Controllers
• Modem
• Stepper Motor
• Key board
• Display
• One for each functional unit sometimes

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Interfacing Examples

1 Generate a square wave on PC0 pin of 8255 in
the add on card Command Word of 8255
7 6 5 4 3
2 1 0
1 MD MD PA PCU
MD PB PCL
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Interfacing Examples

• PPI or Multi Function Devices (MFD) 8255A

PA
D- BF
FN1
C P U
FN2
PB
System Bus
PC
Card
CW Register
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Interfacing Example

• Program
• .MODEL SMALL
• .DATA
• PA EQU 200H
• PB EQU 201H
• PC EQU 202H
• CW WQU 203H

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Interfacing Example

.CODE MOV AX,_at_DATA MOV DS,AX MOV AL,80H
CW MOV DX,CW the addr of CW moved to DX OUT
DX,AL CW sent to MFD Back MOV AL,00H
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Interfacing Example

MOV DX,PC move addr of port c OUT DX,AL CALL
Delay procedure call MOV AL,01H MOV DX,PC OUT
DX,AL CALL Delay JMP Back
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Interfacing Example

Delay PROC MOV CX,0FFFFH Here LOOP
Here RET ENDP END
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Interfacing Example

2 Interface a stepper motor and write program
to rotate in clock-wise direction by N-steps
To all coils of the motor
8255A
Memory
P C 0- 3
CPU
Stepper Motor
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Interfacing Example

• Program
• .MODEL SMALL
• .DATA
• PA EQU 200H
• PB EQU 201H
• PC EQU 202H
• CW WQU 203H

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Interfacing Example

.CODE MOV AX,_at_DATA MOV DS,AX MOV AL,80H
CW MOV DX,CW the addr of CW moved to DX OUT
DX,AL CW sent to MFD MOV CX,64H for the steps
of rotation
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Interfacing Example

MOV AL,88H data to be sent on PC lines MOV
DX,PC load DX with addr of PC Back OUT
DX,AL CALL Delay ROR AL,01H LOOP Back .EXIT
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Interfacing Example

Delay PROC RET ENDP END
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Interfacing Example

3 Interface a 8X3 matrix key pad and write a
program to identify the key closed
.MODEL SMALL .DATA PA EQU 200H PB EQU
201H PC EQU 202H CW WQU 203H
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Interfacing Example

.CODE MOV AX,_at_DATA MOV DS,AX MOV AL,90H
CW MOV DX,CW move addr of CW to DX OUT
DX,AL CW sent to MFD MOV AX,07H MOV DX,PC

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Interfacing Example

OUT DX,AL W1 MOV DX,PA IN AL,DX CMP
AL,00H JZ W1 L1 MOV AH,AL MOV DX,PC OUT DX,AL

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Interfacing Example

MOV DX,PA IN AL,DX CMP AL,00H JNZ C1 ADD
BL,08H MOV AL,0AH RCL AL,01H JMP L1

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Interfacing Example

C1 RCR AL,01H JC L2 INC BL JMP C1 L2 MOV
BL,AL CMP AL,0AH JB Num ADD AL,07H

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Interfacing Example

Num ADD AL,30H MOV DL,AL MOV AH,02H INT
21H MOV AH,4CH INT 21H END