Relocatable Assembly ” files which

(1)

Linking Separately Assembled

“Relocatable” Assembly Files

Up to this point in the course, we have been working with

“

Absolute Assembly

” programs where all code is put into one file,

and it is assembled at absolute addresses indicated with “ORG”

statements.

(2)

•

The need for separately assembly-language modules, which are

separately assembled into object files, and then finally linked together

into a single executable file, may not be very apparent in this course,

where our applications are relatively short and simple.

•

However, in large software development efforts, where several

programmers are involved, it is often more convenient for each

programmer to develop and maintain their own separate program file

which is eventually linked with other programmer’s program files into

an executable program.

•

This approach also shortens compile time, since only the faulty module

(3)

XREF Statement

•

“

XREF variable_list

”

This (XREF => Externally Referenced) statement must appear at the

beginning of any file that references variables or program locations that

are NOT defined in that file. Each of these externally referenced

variables or program locations must be listed following the XREF

keyword.

•

We often say that XREF is used to

IMPORT

variables from other files.

•

XREF is a promise made by the programmer to the linker that the

variables listed can be found in one of the other files that are to be

linked with this one.

(4)

XDEF Statement

•

“

XDEF variable_list

”

This (XDEF => Externally Defined) statement must appear at the beginning of

any file that declares variables or program locations (such as subroutine

names) defined in that file that must be externally referenced by code found

in other files. Each of these locally defined variables or program locations

must follow the XDEF keyword.

•

We often say that XDEF is used to

EXPORT locally defined variables and

program locations

to other files.

•

XDEF is needed to tell the linker that the listed variables or program locations

will need to be accessed by at least one other file that is to be linked with this

one.

•

Example:

(5)

The Linker Parameter File (.PRM)

•

Applications containing relocatable sections must be linked.

The linker parameter file must contain at least:

–

The name of the executable file produced by the linker.

–

The name of the object file(s) which should be linked.

–

The specification of a memory area where the sections containing

variables must be allocated.

–

The specification of a memory area where the sections containing

code or constants must be allocated.

–

The specification of the application's entry point.

(6)

Example of linking three relocatable files

together

•

The first file is named “main.asm”, and it contains a main

program that flashes an LED on and off at a 2-second rate.

•

This main program file “main.asm” calls a timer delay

routine located in a second (separate) file, called

“timer.asm”. This timer routine is called from “main.asm”

by loading the time to wait in a dedicated RAM location

defined back in main.asm file.

•

The “main.asm” file also calls a routine in a third separate

(7)

Steps in setting up the relocatable assembly

project using HC(S)12 CodeWarrior

•

First open CodeWarrior, and click

File – New – HC(S)12 New Project Wizard

•

Enter Project name and desired path

•

Click OK and Next

•

Enter “MC9S12C128” and Next

•

Check “Assembly”, uncheck “C” and Next

(8)

•

Check both “Full-Chip Simulation” and also “P&E Multilink

Cyclone Pro” and Finish.

•

Once this “relocatable assembly” project is created, expand

“PRM”. This contains the linker parameter files that were

created for both the simulator and also for the BDM

download/debugger pod. Select (double left click on) the

“

P&E_Multilink_Cyclone_Pro_linker.prm” file

.

•

Also expand “Sources” and examine the example

(9)

•

This linker parameter file was automatically

generated to link the example relocatable

“main.asm” program that was also

automatically generated.

•

The linked file is then downloaded onto the

CSM12C128 module via the P&E USB BDM

in-circuit background debugging pod that is

(10)

Note the following lines in the .PRM linker

parameter file:

•

NAMES END

(11)

•

SEGMENTS

RAM = READ_WRITE 0x400 to 0x0FFF

(The address range for the 3k RAM block on the 9S12C128 processor

is specified by this line.)

ROM_4000 =READ_ONLY 0x4000 to 0x7FFF

ROM_C000=READ_ONLY 0xC000 to 0xFEFF

(The address ranges for the two 16 kbyte flash ROM (for program

and read-only data) are specified by these lines.)

(12)

•

PLACEMENT

_PRESTART,

STARTUP,

ROM_VAR,

STRINGS,

VIRTUAL_TABLE_SEGMENT,

NON_BANKED,

COPY

INTO ROM_C000 /* or ROM_4000*/

_SSTACK

(13)

•

STACKSIZE 0x100

(this sets the stack segment size to 0x100 bytes, which should

be way more than most programs require. You should

change this if you need a larger stack.)

•

VECTOR 0 Entry

INIT Entry

(This initializes the reset vector (Vector 0) in assembly

programs. The symbol “Entry” corresponds to the symbolic

starting address (entry point) of the main.asm program.

If

(14)

If your ASM file uses interrupts, you will need to initialize the

necessary interrupt vectors just under where the reset vector (Vector

0) is initialized.

•

Note that “Vector 0” (Reset Vector) corresponds to the first entry

in the interrupt table shown on the next slide.

•

For example, if you want to initialize the Timer Channel 2 (TC2)

interrupt vector, to point to an interrupt routine named “TC2_ISR”

you would enter the following two lines at the end of the file:

Vector 10 TC2_ISR

•

IF there are interrupts, also add “ROM_4000” to the

DEFAULT_ROM line of linker PRM file:

(15)

Vector 0



Vector 3



Vector 10



(16)

•

Now click on the “main.asm” file so that it

is displayed in the right window. Erase

the sample file that was automatically

generated, and enter the following

(17)

; export symbols (to be referenced outside of this file)

XDEF Entry

XDEF Timer_word

; import symbols (defined outside of this file)

XREF __SEG_END_SSTACK

XREF WAITMS

XREF INIT_PLL

INCLUDE 'mc9s12c128.inc'

(18)

MyCode: SECTION

Entry:

LDS #__SEG_END_SSTACK ; Initialize the stack pointer

BSET DDRT,$02 ; Make PT1 AN OUTPUT (LED on PT1)

JSR INIT_PLL ; Routine INIT_PLL is in another file

MOVW #1000,Timer_word

FLASHAGN: BSET PTT,$02 ; TURN ON LED

JSR WAITMS ; Routine WTMS is in another file

; Waits number of ms in location

BCLR PTT,$02 ; “Timer_word”

JSR WAITMS

(19)

Adding the INIT_PLL.asm File

•

Now click on

File – New Text File

and enter the following INIT_PLL code on the next slide.

•

When you are done, save the file in your project’s “Sources”

folder, where main.asm is already saved; be sure to name

the file in some meaningful way, giving it an .ASM file

extension, such as “INIT_PLL.asm”

•

Now right click on the “Sources” heading in the left “Project

(20)

; export symbols (to be referenced outside of this file)

XDEF INIT_PLL

MyCode: SECTION

INIT_PLL:

;Initialize clock generator and PLL to increase CPU clock speed by factor of 6

PLL_init bclr CLKSEL,$80 ;Disconnect PLL from system if connected.

bset PLLCTL,$40 ;Turn on the PLL hardware block.

movb #5,SYNR

;Set PLL multiplier

movb #0,REFDV

;Set PLL divider

;From Section 3.1.1 of CRG Block Guide

;PLLCLK = OSCCLK*(SYNR+1)/(REFDV+1)

; = 4 MHz * (5+1)/(0+1) = 24 MHz

nop

;NOP delays put here to allow time for

nop

;CRGFLG flag register to become valid.

wt_PLL_Lock:

brclr CRGFLG, 8, wt_PLL_Lock

;Wait here for PLL to “Lock in”

(21)

Adding the WTMS.asm file

•

Do this in the same way you added the

INIT_PLL file.

(22)

;

export symbols to be referenced outside of this file

XDEF WAITMS

; import external symbols to be referenced inside this file

XREF Timer_word

MY_EXTENDED_RAM: SECTION

TEMPWD: DS.W 1

MyCode: SECTION

WAITMS: PSHY

PSHX

LDY Timer_word

OUTERLOOP: MOVW #5000,TEMPWD

INNERLOOP: LDX TEMPWD

DEX

STX TEMPWD

BNE INNERLOOP

DEY

(23)

Resulting Linker Map File created after

Making this Project:

PROGRAM "C:\Documents and Settings\hoover\Desktop\ECE331

Lecture 6. Relocatable Assembly Modules\reloc_assembly_2009\

bin\P&E_Multilink_CyclonePro.abs"

********************************************

TARGET SECTION

---

---Processor : Freescale HC12

Memory Model: SMALL

(24)

FILE SECTION

--

---main.asm.o

Model: SMALL, Lang: Assembler

INIT_PLL.ASM.o Model: SMALL, Lang: Assembler

WAITMS.ASM.o Model: SMALL, Lang: Assembler

STARTUP SECTION

--

(25)

*****************************************************

**************************************** SECTION-ALLOCATION SECTION

Section Name Size Type From To Segment

---.init 32 R 0xC000 0xC01F ROM_C000

.stack 256 R/W 0x400 0x4FF RAM MyCode 53 R 0x388000 0x388034 PAGE_38 MY_EXTENDED_RAM 4 R/W 0x500 0x503 RAM .vectSeg0_vect 2 R 0xFFFE 0xFFFF .vectSeg0

Summary of section sizes per section type: READ_ONLY (R): 57 (dec: 87) READ_WRITE (R/W): 104 (dec: 260)

********************************************************************************************* VECTOR-ALLOCATION SECTION

Address InitValue InitFunction

0xFFFE 0xC000 Entry

********************************************************************************************* OBJECT-ALLOCATION SECTION

Name Module Addr hSize dSize Ref Section RLIB -MODULE: main.asm.o

--- PROCEDURES:

(26)

- PROCEDURES:

INIT_PLL 388000 13 19 1 MyCode wt_PLL_Lock 388013 8 8 0 MyCode - VARIABLES:

MODULE: WAITMS.ASM.o --- PROCEDURES:

WAITMS 38801B 5 5 2 MyCode OUTERLOOP 388020 6 6 0 MyCode INNERLOOP 388026 F 15 0 MyCode - VARIABLES:

TEMPWD 502 2 2 3 MY_EXTENDED_RAM

********************************************************************************************* MODULE STATISTIC

Name Data Code Const

main.asm.o 2 32 0

INIT_PLL.ASM.o 0 27 0 WAITMS.ASM.o 2 26 0 other 256 2 0

********************************************************************************************* SECTION USE IN OBJECT-ALLOCATION SECTION

---SECTION: ".init"

Entry FLASHAGN SECTION: "MyCode"

INIT_PLL wt_PLL_Lock WAITMS OUTERLOOP INNERLOOP SECTION: "MY_EXTENDED_RAM"

(27)

********************************************************************************************* OBJECT LIST SORTED BY ADDRESS

Name Addr hSize dSize Ref Section RLIB Timer_word 500 2 2 2 MY_EXTENDED_RAM TEMPWD 502 2 2 3 MY_EXTENDED_RAM Entry C000 10 16 0 .init

FLASHAGN C010 10 16 0 .init INIT_PLL 388000 13 19 1 MyCode wt_PLL_Lock 388013 8 8 0 MyCode WAITMS 38801B 5 5 2 MyCode OUTERLOOP 388020 6 6 0 MyCode INNERLOOP 388026 F 15 0 MyCode

********************************************************************************************* UNUSED-OBJECTS SECTION ---********************************************************************************************* COPYDOWN SECTION ---********************************************************************************************* OBJECT-DEPENDENCIES SECTION ---Entry USES __SEG_END_SSTACK INIT_PLL Timer_word

FLASHAGN USES WAITMS WAITMS USES Timer_word OUTERLOOP USES TEMPWD INNERLOOP USES TEMPWD

(28)

Making and Downloading this program

onto the CSMB9S12C128

•

LED on PT1 blinks at a 2 second rate

•

Commenting out the JSR INIT_PLL and remaking and

downloading results in an LED on PT1 that blinks at

a 24 second rate, because the bus clock has now

been lowered from