The following questions are set up in view of the figures (a,b). a) Describe what type of I/O operation is carried out in Figure (a). Write an instruction sequence that will input the byte contents of input port 6 to memory location MEM1. b) What is the polling operation? Write a sequence of instructions to poll the input 17 at input port 5 to check whether it is switched to zero or not. Figure (a). c) Write a sequence of instructions that will read the contents of input port 7. Mask off all the bits except LSB. The content of LSB will be shifted to CF. If CF =1, then the program will go to start of service routine XXX. Figure (a). d) Describe what type of 1/0 operation is carried out in Figure (b). Write a sequence of instructions to initialize the control register in PPI 0 in Figure (b) so that PA is an output port, PB and Pc are input ports. Initialize all the necessary registers. Ports are configured for mode O operation. e) Write a program to input the contents of PB and Pc then OR them together and send the resultant to PA. These ports are the PPI O ports in Figure (b). Ports are configured for mode 0 operation. Initialize all the necessary registers. Write comments and Use minimum number of instructions in your programs. ALE CLK Aai-Aise AD-AD, A-AS 74F373 (2) Address latch OE A Au D P. CBA 74F138 G Input/ P Output Gaddress decoder G 74F244 Port 0 10/M 8088 MPU 1 D-D AD, AD 74F245 Data bus transceiver DIR G DT/R 19 74F244 Port 1 DEN G RD D G 74F244 Port 7 Figure (a) Figure 7.12 Sixty-four-line input circuit for an 8088 microcomputer. Control bus Address bus Ag-Ag Data bus Do-D ob- As A 2212 B 14 74F138 GB To other even address peripheral 10 10/M 8 GA 6 Aio G IN 0 CS Port A D-D1 D-D A A, 8255A Port C Az A RD RD WR Port B WR Figure 7.27 Memory-mapped 8255A 10 ports in an 8088 microcomputer, Figure (b) The following questions are set up in view of the figures (a,b). a) Describe what type of I/O operation is carried out in Figure (a). Write an instruction sequence that will input the byte contents of input port 6 to memory location MEM1. b) What is the polling operation? Write a sequence of instructions to poll the input 17 at input port 5 to check whether it is switched to zero or not. Figure (a). c) Write a sequence of instructions that will read the contents of input port 7. Mask off all the bits except LSB. The content of LSB will be shifted to CF. If CF =1, then the program will go to start of service routine XXX. Figure (a). d) Describe what type of 1/0 operation is carried out in Figure (b). Write a sequence of instructions to initialize the control register in PPI 0 in Figure (b) so that PA is an output port, PB and Pc are input ports. Initialize all the necessary registers. Ports are configured for mode O operation. e) Write a program to input the contents of PB and Pc then OR them together and send the resultant to PA. These ports are the PPI O ports in Figure (b). Ports are configured for mode 0 operation. Initialize all the necessary registers. Write comments and Use minimum number of instructions in your programs. ALE CLK Aai-Aise AD-AD, A-AS 74F373 (2) Address latch OE A Au D P. CBA 74F138 G Input/ P Output Gaddress decoder G 74F244 Port 0 10/M 8088 MPU 1 D-D AD, AD 74F245 Data bus transceiver DIR G DT/R 19 74F244 Port 1 DEN G RD D G 74F244 Port 7 Figure (a) Figure 7.12 Sixty-four-line input circuit for an 8088 microcomputer. Control bus Address bus Ag-Ag Data bus Do-D ob- As A 2212 B 14 74F138 GB To other even address peripheral 10 10/M 8 GA 6 Aio G IN 0 CS Port A D-D1 D-D A A, 8255A Port C Az A RD RD WR Port B WR Figure 7.27 Memory-mapped 8255A 10 ports in an 8088 microcomputer, Figure (b)
