1203 Ppi 8155
- 1. Programmable Peripheral Interface Devices Support chips : 8155 , 8255 , 8279, 8254 , DMA Controller, Interrupt Controller, USART
- 2. Programmable Interface Devices used to interface a I/O device to the microprocessor 8085 Programmable I/O Interface I/O Devices System Bus
- 3. 8155 – A multipurpose programmable interface Designed to be compatible with 8085 It includes 256 bytes of Read/Write memory Three I/O ports Port A Port B Port C A 14-bit timer
- 4. Block Diagram - 8155 256 X 8 Static RAM A B C Timer 8 8 6 Port A Port B Port C PA 0-7 PB 0-7 PC 0-5 8 AD 0-7 IO/M CE ALE RD WR Timer CLK TIMER OUT Vcc (+5 V) Vss (0 V) RESET I/O Devices 8085
- 5. Application design with 8155 Objectives Interfacing 8155 with 8085 Programming 8155
- 6. Interfacing 8085 with 8155 8085 256 X 8 Static RAM A B C Timer 8 8 6 Port A Port B Port C 8 AD 0-7 IO/M CE ALE RD WR RESET A 15 8085 8155
- 7. Programming 8155 8155 is a Programmable Peripheral Interface 8085 can send data to 8155 using data bus This data can be For I/O devices connected to 8155 Timer registers of 8155 Instruction/ Command word for 8155 Commands for 8155 are stored in a 8-bit Control Register inside 8155
- 8. What type of Commands can be given to 8155? To configure the I/O ports as Input or Output To start/stop timer etc. To use handshake mode or not
- 9. Control word for 8155 A command/instruction for 8155 is also called control word This control word is written to control register of 8155 Control word of 8155 is of 8-bits
- 10. Control Word Definition for 8155 Port A Port B 0, Input 1, Output Port C Interrupt Enable Port A Interrupt Enable Port B 0, Disable 1, Enable Timer D0 D1 D2 D3 D4 D5 D6 D7 D3 D2 PORT C 0 0 ALT1 0 1 ALT2 1 0 ALT3 1 1 ALT4 D7 D6 Timer 0 0 NOP 0 1 Stop 1 0 Stop after TC 1 0 Start
- 11. I/O functions of Port C I = Input O = Output STB = Strobe BF = Buffer Full INTR = Interrupt Request ALT D3 D2 PC5 PC4 PC3 PC2 PC1 PC0 ALT1 0 0 I I I I I I ALT2 0 1 O O O O O O ALT3 1 0 O O O STB A BF A INTR A ALT4 1 1 STB B BF B INTR B STB A BF A INTR A
- 12. Design an interfacing circuit to read data from an A/D converter using the 8155A in the peripheral mapped I/O . 8085 3-to-8 Decoder A/D Converter Analog Input Digital Input Por t A AD0-AD7 O 0 O 7 8155 Por t C Por t B SOC OE EOC O 2 CE E 2 E 1 A 2 A 1 A 0 A 11 A 12 A 13 A 14 A 15 IO/M RD WR RESET ALE LED Display BF A STB A PC5
- 13. Port Addresses of 8155 Chip Selection A7 A6 A5 A4 A3 0 0 0 1 0 = 10H = 11H = 12H = 13H = 14H = 15H A2 A1 A0 Port 0 0 0 Control/Status Register 0 0 1 Port A 0 1 0 Port B 0 1 1 Port C 1 0 0 LSB Timer 1 0 1 MSB Timer
- 14. Application Programming Logic Configure 8155 8085 sends SOC command to ADC 8085 communicates with ADC using PortC in handshake mode 8085 reads 8-bit temperature value from port A 8085 displays the temperature value on the LED display
- 15. 1. Configure 8155 I/O Ports Port A as INPUT port Port B as OUTPUT port Port C in ALT3 mode SOC EOC OE ALT D3 D2 PC5 PC4 PC3 PC2 PC1 PC0 ALT3 1 0 O O O STB A BF A INTR A
- 16. Control Word for configuration Port A Port B 0, Input 1, Output Port C IE Port A IE Port B 0, Disable 1, Enable Timer D0 D1 D2 D3 D4 D5 D6 D7 D3 D2 PORT C 0 0 ALT1 0 1 ALT2 1 0 ALT3 1 1 ALT4 D7 D6 Timer 0 0 NOP 0 1 Stop 1 0 Stop after TC 1 0 Start 0 1 0 1 0 0 0 0
- 17. Program Instructions for configuration Data Control word : 0A H Port Address Address of Control register : 10 H Instructions MVI A, 0A H OUT 10 H
- 18. 2. 8085 sends SOC command to ADC A small duration pulse on SOC input of ADC will start conversion process SOC input of ADC is connected to port pin PC5 of Port C (Port address 13 H) Data Data value 20 H followed by 00 H SOC ALT D3 D2 PC5 PC4 PC3 PC2 PC1 PC0 ALT3 1 0 O O O STB A BF A INTR A 1 0 0 0 0 0
- 19. Instructions Start: MVI A, 20H OUT 13H MVI A, 00H OUT 13H
- 20. 3. 8085 communicates with ADC using Port C in handshake mode Port A used to input 8-bit data from ADC Port C used for handshaking EOC OE ALT D3 D2 PC5 PC4 PC3 PC2 PC1 PC0 ALT3 1 0 O O O STB A BF A INTR A
- 21. ADC resets EOC to LOW at end of conversion 8155 sets BF to 1 to enable ADC output latch 8085 is waiting for BF to be SET to 1 and Reads port A by making RD signal active ( 0 ) At the end of read cycle RD goes HIGH ( 1 ) This resets BF signal to 0 . 8085 waits for BF signal to be RESET and starts conversion process again
- 22. 8085 is waiting for BF To know the status of BF signal 8085 reads status register of 8155 Status register shares same address as control register Status Word Definition X Timer INTEB BFB INTRB INTEA BFA INTRA D7 D6 D5 D4 D3 D2 D1 D0
- 23. Program Instructions 8085 reads status register Address of status register : 10H Reads port A if BFA = 1 Output temperature on port B Status: IN 10H ANI 02H JZ Status IN 11H ; Step -4 Reads temperature value OUT 12H ; Step –5 display on LED’s
- 24. 8085 reads status register Address of status register : 10H Starts conversion again if BFA = 0 Again: IN 10H ANI 02H JNZ Again JMP Start
- 25. Complete Program MVI A, 0A H OUT 10 H Start: MVI A, 20H OUT 13H MVI A, 00H OUT 13H Status: IN 10H ANI 02H JZ Status IN 11H OUT 12H Again: IN 10H ANI 02H JNZ Again JMP Start Configure 8155 Start Conversion Read Status register Wait till BF A = 1 Read temperature value Display on LED Read status register Wait till BF A = 0 Start Conversion again
Editor's Notes
- #11: 00000111 07h