ECE251: Thursday September 13

Transcription

1 ECE251: Thursday September 13 Lab 9: Some Details Stack and Subroutines, continued--chapter 8 Stack Example SUBROUTINES More Details Initializing the Stack/Pointer Passing Parameters to Subroutines via Registers Homework #2 is due today at 4 pm Homework #3 will be due in two weeks- Sept. 27 Lab 3 continues next week. Lab 4 online soon. Mid-Term Exam is 3 weeks from today: October 4 Practical Exam 1 is week of October 8 during lab 1

2 Lab 9: Independent Lab Project Objectives: This lab will give you the opportunity to apply your understanding of the TM4C processor to creating and completing an independent project. In this lab, you will learn: How to evaluate possible projects by your interest and your likely ability to complete that project. How to manage your time on a project that can span half a semester or more. How to document your lab results in the form of a project description that future students could use. More about some specific technology, based on your project choice. HAVE FUN with this project! 2

3 Lab 9: Input Device Ideas Input Devices and units on hand Microphone Sensor Module: Amazon: DAOKI High Sensitivity Sound Microphone Sensor Detection Module KY-037 Module(PDF) Water Level Sensor GPS Module Data Sheet(PDF) Amazon: Water Sensor AliExpress: GY-NEO6MV2 NEO-6 Data Sheet 60 KHz WWVB Receiver Amazon: Receiver MAS6180C Data Sheet Plus much more online info Tilt Ball Switch Sensor 4+ Units oddwires: Tilt/Ball Switch Sensor Amazon: Gikfun Tilt Switch Sensor Infrared Body Motion Sensor Amazon: Gowoops HC-SR501 Ultrasonic Distance Sensor 3

4 Lab 9: Output Device Ideas Output Devices and units on hand LED Single Color Many Units Amazon: LEDs with resistors LED RGB Many Units Kingbright Full Color LED (PDF) LED Matrix Display Driver 4 Units MAX7219 8x8 Display (PDF) LED Display Driver Active Buzzer 5 v. 4+ Units Amazon: CYT1036 Cylewet 5v. Active Buzzer Instructables: How to Use a Buzzer Passive Buzzer 3-12 v. 5 V Relay Module Amazon: KY-019 CHENBO 1Channel Relay Module 1 Digit 7-Segment Display Many Units Jameco Tech Tips User Manual (PDF) Stepper Motors 5 Units 4

5 Lab 9: Next Steps Create a Written Project Proposal for TA Discussion Week after Practical #1; i.e. week of October 15 No Particular Proposal Structure Required Basis for Creating a Project Commitment a few weeks later Use Online Course Documents regarding Project Options and Device Ideas This Proposal Will be 10% of your Lab 9 Grade Spend some time and thought on this Discuss with your TA and/or Instructor and/or Grader Be sensitive to possible difficulty with project. Keep it relatively simple. Will be easy to add to it later (with TA approval). 5

6 Review: Calling a Subroutine BL label (Branch and Link) Step 1: LR = PC + 4 Step 2: PC = label Notes: label is name of subroutine Assembler translates label to memory address After call, LR holds return address (the instruction following the BL instruction) Caller Program MOV r4, # BL foo... Subroutine/Callee foo... MOV r4, #

7 Review: Exiting a Subroutine (Branch and Exchange) PC = LR Caller Program MOV r4, # BL foo... Subroutine/Callee foo... MOV r4, #

8 Subroutine Calling Another Subroutine MAIN QUAD PUSH {LR} Function MAIN Function QUAD Function What s happening in this code? What s at ENDL? Why did we PUSH and later POP register LR in Subroutine QUAD? This is a KEY concept! 8

9 Subroutine Calling Another Subroutine MAIN QUAD PUSH {LR} Function MAIN Function QUAD Function 9

10 Example: = 4 xxxxxxxx 0x x200001FC 0x200001F8 0x x C QUAD PUSH {LR} SP LR PC 0x x QUAD PUSH {LR} 0x x x x A 0x E 0x x

11 Example: = 4 xxxxxxxx 0x x200001FC 0x02 0x200001F8 0x x C QUAD PUSH {LR} SP LR PC 0x x C QUAD PUSH {LR} 0x x x x A 0x E 0x x

12 Example: = 4 xxxxxxxx 0x x200001FC 0x02 0x200001F8 0x x C QUAD PUSH {LR} SP LR PC 0x x Preserve Link Register (LR) QUAD PUSH {LR} 0x x x x A 0x E 0x x

13 Example: = 4 xxxxxxxx 0x x200001FC 0x02 0x200001F8 0x x C QUAD PUSH {LR} SP LR PC 0x200001FC 0x A QUAD PUSH {LR} 0x x x x A 0x E 0x x

14 Example: = 4 xxxxxxxx 0x x200001FC 0x02 0x200001F8 0x x C QUAD PUSH {LR} SP LR PC 0x200001FC 0x E 0x QUAD PUSH {LR} 0x x x x A 0x E 0x x

15 Example: = 4 xxxxxxxx 0x x200001FC 0x04 0x200001F8 0x x C QUAD PUSH {LR} SP LR PC 0x200001FC 0x E 0x QUAD PUSH {LR} 0x x x x A 0x E 0x x

16 Example: = 4 xxxxxxxx 0x x200001FC 0x04 0x200001F8 0x x C QUAD PUSH {LR} SP LR PC 0x200001FC 0x E 0x E QUAD PUSH {LR} 0x x x x A 0x E 0x x

17 Example: = 4 xxxxxxxx 0x x200001FC 0x04 0x200001F8 0x x C QUAD PUSH {LR} SP LR PC 0x200001FC 0x x QUAD PUSH {LR} 0x x x x A 0x E 0x x

18 Example: = 4 xxxxxxxx 0x x200001FC 0x10 0x200001F8 0x x C QUAD PUSH {LR} SP LR PC 0x200001FC 0x x QUAD PUSH {LR} 0x x x x A 0x E 0x x

19 Example: = 4 xxxxxxxx 0x x200001FC 0x10 0x200001F8 0x x C QUAD PUSH {LR} SP LR PC 0x200001FC 0x x QUAD PUSH {LR} 0x x x x A 0x E 0x x

20 Example: = 4 xxxxxxxx 0x x200001FC 0x10 0x200001F8 0x x C QUAD PUSH {LR} SP LR PC 0x x Recover Link Register (LR) QUAD PUSH {LR} 0x x x x A 0x E 0x x

21 Example: = 4 xxxxxxxx 0x xxxxxxxx 0x200001FC 0x10 0x200001F8 0x x C QUAD PUSH {LR} SP LR PC 0x QUAD PUSH {LR} 0x x x x A 0x E 0x x

22 Initializing the Stack/Pointer Before USING the Stack, that block of memory must be reserved, and the STACK POINTER (SP) initialized to point to the appropriate address in R/W memory. The TM4C Processor doesn t know where it will be. The uvision software doesn t know where it will be. Your program doesn t need to know where it will be! This is handled by the Startup.s file you import into your project. It creates a 0x400 byte stack with the appropriate initial value for SP for this stack. See some sample code following. Startup is similar. Check it next time you run your software with Vision! Hint: This could be a homework or quiz question! 22

23 Initializing stack in startup code ; Stack Area ;*************************************************************** ;LABEL DIRECTIVE VALUE COMMENT Stack EQU 0x ; stack size AREA STACK, NOINIT, READWRITE, ALIGN=3 StackMem SPACE Stack ;*************************************************************** ; Reset Area ;*************************************************************** ;LABEL DIRECTIVE VALUE COMMENT AREA RESET, CODE, READONLY THUMB Vectors EXPORT Vectors DCD StackMem + Stack ; Top of Stack DCD Reset_Handler ; Reset Handler ;*************************************************************** 23

24 Register ARM Procedure Call Standard Interesting, but not key information in ECE 251 Usage Subroutine Preserved r0 Argument 1 and return value No Notes If return has 64 bits, then r0:r1 hold it. If argument 1 has 64 bits, r0:r1 hold it. r1 Argument 2 No r2 Argument 3 No If the return has 128 bits, r0-r3 hold it. r3 Argument 4 No If more than 4 arguments, use the stack r4 General-purpose V1 Yes Variable register 1 holds a local variable. r5 General-purpose V2 Yes Variable register 2 holds a local variable. r6 General-purpose V3 Yes Variable register 3 holds a local variable. r7 General-purpose V4 Yes Variable register 4 holds a local variable. r8 General-purpose V5 YES Variable register 5 holds a local variable. r9 Platform specific/v6 No Usage is platform-dependent. r10 General-purpose V7 Yes Variable register 7 holds a local variable. r11 General-purpose V8 Yes Variable register 8 holds a local variable. r12 (IP) Intra-procedure-call register No It holds intermediate values between a procedure and the sub-procedure it calls. r13 (SP) Stack pointer Yes SP has to be the same after a subroutine has completed. r14 (LR) Link register No LR does not have to contain the same value after a subroutine has completed. r15 (PC) Program counter N/A Do not directly change PC 24

25 Procedure Call Standard Low Registers 32 bits R1 R2 R3 R4 Not saved. Hold arguments, results, or temporary values. Caller shouldn t expect them to be retained. R5 R6 R7 R8 General Purpose Register Called must save them. Caller expects these values are retained. High Registers R9 R10 R11 32 bits xpsr Link Register R12 R13 (SP) R14 (LR) R15 (PC) R13 (MSP) R13 (PSP) BASEPRI PRIMASK FAULTMASK CONTROL Special Purpose Register 25

26 Example: R2 = *+R1*R1 (Inner Product) S... MUL R2,, MUL R3,R1,R1 ADD R2,R2,R

27 Passing Arguments to Subroutine via Registers Example: z = x 2 + y 2 S MUL R2,, MUL R3,R1,R1 ADD R2,R2,R3 R1 R2 R3 LR PC 0x S MUL R2,... MUL R3,... ADD R2,R3 Memory Address 0x x C 0x x x x C 0x x x x A 27

28 Passing Arguments to Subroutine via Registers Example: z = x 2 + y 2 S MUL R2,, MUL R3,R1,R1 ADD R2,R2,R3 R1 R2 R3 LR 3 PC 0x S MUL R2,... MUL R3,... ADD R2,R3 Memory Address 0x x C 0x x x x C 0x x x x A 28

29 Passing Arguments to Subroutine via Registers Example: z = x 2 + y 2 S MUL R2,, MUL R3,R1,R1 ADD R2,R2,R3 R1 R2 R3 LR 3 4 PC 0x C S MUL R2,... MUL R3,... ADD R2,R3 Memory Address 0x x C B 0x x x x C 0x x x x A 29

30 Passing Arguments to Subroutine via Registers Example: z = x 2 + y 2 S MUL R2,, MUL R3,R1,R1 ADD R2,R2,R3 R1 R2 R3 LR 3 4 PC 0x S MUL R2,... MUL R3,... ADD R2,R3 Memory Address 0x x C 0x x x x C 0x x x x A 30

31 Passing Arguments to Subroutine via Registers Example: z = x 2 + y 2 S MUL R2,, MUL R3,R1,R1 ADD R2,R2,R3 R1 R2 R3 Address of the next instruction after the branch is saved into LR. 3 4 LR 0x PC 0x C S MUL R2,... MUL R3,... ADD R2,R3 Memory Address 0x x C 0x x x x C 0x x x x A 31

32 Passing Arguments to Subroutine via Registers Example: z = x 2 + y 2 S MUL R2,, MUL R3,R1,R1 ADD R2,R2,R3 R1 R2 R LR 0x PC 0x C S MUL R2,... MUL R3,... ADD R2,R3 Memory Address 0x x C 0x x x x C 0x x x x A 32

33 Passing Arguments to Subroutine via Registers Example: z = x 2 + y 2 S MUL R2,, MUL R3,R1,R1 ADD R2,R2,R3 R1 R2 R LR 0x PC 0x S MUL R2,... MUL R3,... ADD R2,R3 Memory Address 0x x C 0x x x x C 0x x x x A 33

34 Passing Arguments to Subroutine via Registers Example: z = x 2 + y 2 S MUL R2,, MUL R3,R1,R1 ADD R2,R2,R3 R1 R2 R LR 0x PC 0x S MUL R2,... MUL R3,... ADD R2,R3 Memory Address 0x x C 0x x x x C 0x x x x A 34

35 Passing Arguments to Subroutine via Registers Example: z = x 2 + y 2 S MUL R2,, MUL R3,R1,R1 ADD R2,R2,R3 R1 R2 R LR 0x PC 0x S MUL R2,... MUL R3,... ADD R2,R3 Memory Address 0x x C 0x x x x C 0x x x x A 35

36 Passing Arguments to Subroutine via Registers Example: z = x 2 + y 2 25 R1 4 R2 25 R3 16 LR 0x Memory Address 0x x C 0x S MUL R2,, MUL R3,R1,R1 ADD R2,R2,R3 PC 0x A S MUL R2,... MUL R3,... ADD R2,R3 0x x x C 0x x x x A 36

37 Passing Arguments to Subroutine via Registers Example: z = x 2 + y 2 S MUL R2,, MUL R3,R1,R1 ADD R2,R2,R3 R1 R2 R3 Copy LR to PC when returning from a subroutine! LR 0x PC 0x S MUL R2,... MUL R3,... ADD R2,R3 Memory Address 0x x C 0x x x x C 0x x x x A 37

38 Passing Arguments to Subroutine via Registers Example: z = x 2 + y 2 S MUL R2,, MUL R3,R1,R1 ADD R2,R2,R3 R1 R2 R LR 0x PC 0x S MUL R2,... MUL R3,... ADD R2,R3 Memory Address 0x x C 0x x x x C 0x x x x A 38

39 Passing Arguments to Subroutine via Registers Example: z = x 2 + y 2 S MUL R2,, MUL R3,R1,R1 ADD R2,R2,R3 R1 R2 R LR 0x PC 0x S MUL R2,... MUL R3,... ADD R2,R3 Memory Address 0x x C 0x x x x C 0x x x x A 39

40 For Loop sum=0 For i=0 to 10 sum=sum+i MOV r0, #0 ; i MOV r1, #0 ; sum loop endloop CMP r0, #10 ; ; 10 is loop limit BGE endloop ADD r1, r1, r0 ADD r0, r0, #1 B loop What is value in r1 when program gets to endloop? 40

41 While C then S Loop Construct loop CMP {Boolean comarison C} B{false} endloop ; execute instructions S here B loop endloop 41

42 Repeat S until C Loop Construct loop ; execute instructions S here endloop B{Condition C true} loop 42

43 Some Helpful Suggestions RTT*! It has important information and helpful examples. It will make a difference in understanding! Read the labs! Don t just skip to the lab procedures. The lab write-up has important information and will usually include lab prework. Read the lecture slides! They have useful examples. I.e. Start becoming a professional engineer using the key sources available to you! * Read The Textbook 43

44 Summary Lab #9 Intro Initializing the Stack space and SP Saving LR when needed Passing Parameters to subroutines via stack Next Lecture: Subroutines and passing info Recursive subroutines Debugging HW and SW 44