ES C263 Microprocessor Programming and Interfacing Pawan Sharma Lecture 3 10-01-2013

Last Lecture Instruction Set Architecture

Today’s Lecture Design Example PC Boot Process

Design Example

Design a microprocessor based system to control pH of a solution in a reactor tank. User enters desired pH (0-14) and controller gain Reactor tank is provided with three pH sensors, to compute the average pH. Reactor tank has three inputs. (acid flow, base flow effluent discharged from factory controlled by valves) Motorised valve

Valve Control Controlled by stepper motors 1 step is by 1.8 degrees rotation Valve opening = kP * error Where error = desired pH – measured pH. Error positive- close fully acid valve and open base valve accordingly Error negative- close fully base valve and open acid valve accordingly. 0 – 360 degrees correspond to 0 to 200 steps.

Stepper Motor sequence: A B C D 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 1 0 1 0 0 1 1 0 0 1 0 1 1 0 0 1 ACW CW Use a 4- bit port + driver (nearly 1 A current)

pH sensor Vout pH 7 14 Voltage output 60mV/pH -420mV - +420mV

Interfacing Analog to Digital Converter 8-bit ADC I0 I7 D0 D7 Start A B C EOC OE ALE ADC 0809

Input Keys Numeric keys 0 – 9 Function keys pH, kP, enter Matrix Keypad interfacing!! - 2 four bit ports.

Display Device and storage Two digit Display Two seven segment display devices to display pH Memory Interfacing ROM (4KB) - FF000H – FFFFFH SRAM (4K) - 00000H – 00FFFH

System Block Diagram CPU Memory I/O Interface Parallel I/O Serial I/O Data Address Control

Method of Approach Identify input and output devices Memory requirements Suitable memory and I/O interfacing Assembly Language Programming Assumptions made

PC Boot Process

The code performs POST (Power On Self test) Powered on CPU starts executing code located from FFFF0H – called BIOS and operates in the real mode of operation. The code performs POST (Power On Self test) After POST, CPU reads the boot sector (floppy, hard disk – sequence set in BIOS features)‏ Checks for AA55H at 07DFEH --- ( Boot signature)‏ The first sector of the bootable disk, contains the boot loader program or the MBR or grub/LILO. The BIOS loads the MBR in RAM starting at address 07C00H and executed. Loads DL (one of the CPU registers) with 00h if the boot sector was loaded from drive A 80h if the boot sector was loaded from drive C This way, the bootsector can determine which drive it was booted from. After the completion of the boot loader program, the control is transferred to the OS.