Programming - Introduction to Microprocessor Systems - Lecture Sli, Lecture notes of Computer Science

Download Programming - Introduction to Microprocessor Systems - Lecture Sli and more Lecture notes Computer Science in PDF only on Docsity! • ARM7TDMI Programming – LUTs – Branches and Loops • Structured Programming – Flowcharts • Stacks – Hardware versus Memory Stacks – ARM7TDMI Stack Management Topics Docsity.com Look-Up Tables • In an embedded system, the code area is usually in nonvolatile memory (ROM) • Data in the code area will also be placed in ROM – so the data is constant • Look-up tables (LUTs) are used to translate a value from one domain to another when… – There is no convenient mathematical relationship between the two domains – The calculations are too expensive for the application constraints Docsity.com Conditional Branches and Looping • Conditional branches allow program flow to change in response to conditions – Action is based on current state of flags – Prior instruction must be used to set flags • Can use backwards conditional jumps to create a loop that can be terminated - – By a condition – After a predetermined number of iterations – Or a combination of both • Looping examples – Incrementing loops – Decrementing loops Docsity.com Implementing Structured Programming Constructs • Structured programming basics – One entry point, one exit point per subroutine – Based on three basic control structures • Sequence • Selection – If, If/Else, Switch/Case • Repetition – While – Do-While • Flowchart Basics • Programming Exercise Docsity.com Stack Implementation • The stack is a LIFO data structure • What is the stack used for? • Two basic stack operations – PUSH – POP (aka PULL) • Hardware stacks vs. memory stacks – Hardware stack – Memory stack • Stack pointer (SP) • Stack topologies and SP operation Docsity.com PIC16F84 Hardware Stack FIGURE 1-1: PIC16F84A BLOCK DIAGRAM DataBus 8 13, Program Counter EEPROM Data Memory FLASH Program Memory RAM EEPROM 8 Level Stack =p} EEDATA >| Data Memory| 1K x14 ean File Registers a Mer 68x8 Program ‘t Bus 4|"4 EEADR Instruction Register TMRO RAA/TOCKI 8 Power-up , Thnor VO Ports Instruction Oscillator L Decode & K—=> | Start-up Timer contro Power-on RA3:RAO ase me Timing Watchdog =X] Re7:R81 Generation >} Timer b a DX] Reoant OSC2/CLKOUT MCLR — Vbb, Vss OSC1/CLKIN Docsity.com Jump Tables start MOV R0, ??? ; assume index is in R0 ADR R1, jmptbl ; get base address LDR R0, [R1,R0,LSL #2] ; do look-up BX R0 ; branch to target ; task0 ; stub NOP B start ; task1 ; stub NOP B start ; jmptbl DCD task0, task1; ... Docsity.com B Instruction Reference • Syntax – B{<cond>} <target_address> • RTL – if (cond is true) • PC  PC + offset • Flags are not affected 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 cond 1 0 1 0 signed_immediate_24 Docsity.com