ME4447/6405 Microprocessor Control of Manufacturing Systems and Introduction to Mechatronics

ME4447/6405 Assembly Language Format (Note: Last three options are called Operands ) A Tab (8 white spaces) or Label (Note: A Label is another Assembly Directive and will be covered in later lectures) Assembly Directive Or Mnemonic Instruction Data that the Assembly Directive uses Or Blank if Mnemonic Instruction does not need Data Or Offset Address used to modify Program Counter by a Mnemonic Instruction Or Data that Mnemonic Instruction uses Or Address where the Data that Mnemonic Instruction will use is stored The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Front ORG LDAA DECA BNE LDAB STAB INCX SWI END $0800 #$100A Front $2F,Y $110C 86 43 27 3F 100A 0E The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Addressing Modes In the previous slide, there were several options for the operand : • Blank if Mnemonic Instruction does not need Data • Offset Address used to modify Program Counter by a Mnemonic Instruction • Data that Mnemonic instruction uses • Address were Data that Mnemonic instruction uses is stored Which option a programmer uses is defined by the following addressing modes : ( See next slide also) •Inherent •Immediate •Extended •Indexed Indirect •Direct •Indexed •Relative (Note: All instructions are not capable of all addressing modes. Example: BLE [ B ranch if L ess than or E qual to Zero] is only capable of Relative addressing mode) The George W. Woodruff School of Mechanical Engineering

ME4447/6405 The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Example: Programming Reference Guide Page 6 The George W. Woodruff School of Mechanical Engineering

ME4447/6405 The George W. Woodruff School of Mechanical Engineering

ME4447/6405 The George W. Woodruff School of Mechanical Engineering

ME4447/6405 The George W. Woodruff School of Mechanical Engineering

ME4447/6405 The George W. Woodruff School of Mechanical Engineering

ME4447/6405 The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Blank if Mnemonic Instruction does not need Data If Mnemonic Instruction does not need data then it uses Inherent Addressing Mode Example: Write a program to clear accumulator A. Start programming at address $1000

Solution:

ORG $1000 CLRA SWI END CLRA [ CL ea R accumulator A ] is an instruction using Inherent Addressing (NOTE: SWI [ S oft W are I nterrupt] is a mnemonic instruction which tells the 9SC32 to store the content of cpu registers on the stack. Sets the I bit (the interrupt bit) on the CCR. Loads the program counter with the address stored in the SWI interrupt vector, and resume program execution at this location. If no address is stored in the SWI vector, the main program will stop execution at this point. Used in this course to return control to Mon12 Program )

ME4447/6405 Data that Mnemonic instruction uses The Mnemonic instruction is using Immediate Addressing mode if the operand is Data used by the instruction Example: Write a program to load accumulator A with #$12. Start programming at address $1000

Solution:

ORG $1000 LDAA #$12 SWI END LDAA #$5BEE (Explain what happens) LDAA is an instruction using Immediate Addressing mode in this example The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Address were Data that Mnemonic instruction uses is stored The following addressing modes apply if the operand is an Address containing Data used by Mnemonic instruction : Direct •Data is contained in Memory locations $00 to $FF •Address is given as a single byte address between $00 to $FF •Instructions using Direct addressing has fastest access to memory Example: LDAA $00 Loads accumulator A with Data value stored at memory location $00 Extended •Data is contained in Memory locations $0100 to $FFFF •Address is given as a two byte address between $0100 to $FFFF Example: LDAA $2000 Loads accumulator A with Data value stored at memory location $2000 The George W. Woodruff School of Mechanical Engineering

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Example Problem 1

Example : Write a program to add the numbers 10 10 and 11 10 .

Solution

ORG LDAA LDAB ABA STAA SWI END $1000 #$0A #$0B $00 *Puts number $0A in acc. A *Puts number $0B in acc. B *Adds acc. B to acc. A *Stores results in address $00 *Software interrupt LDAB and LDAA use immediate addressing mode STAA uses direct addressing mode The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Address were Data that Mnemonic instruction uses is stored (Continued) Indexed: • Data is located within Memory locations $00 to $FFFF Example: Store content of $2003 in Register A LDX #$2000 LDAA $03,X Loads accumulator A with Data value stored at memory location $2003 X + $03 = $2000 + $03 = $2003 (Note: LDX [ L oa D index register X ]) The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Why is Indexed Addressing Mode needed?

Example: Store Data Value #$20 into memory locations $2000 to $3000 Without Indexed Addressing Mode ORG $1000 LDAA #$20 STAA $2000 STAA $2001 SWI END .

.

.

STAA $3000 With Indexed Addressing Mode LOOP ORG $1000 LDAA #$20 LDX #$2000 STAA $00,X INX CPX #$3001 BNE LOOP SWI END Program on the Left is much longer than program on Right The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Why is Indexed Addressing Mode needed? (Continued) LOOP ORG $1000 LDAA #$20 LDX #$2000 STAA $00,X INX CPX #$3001 BNE LOOP SWI END Note: LDAA[ L oa D accumulator A ] LDX [ L oa D I ndex Register X ] STAA [ ST ore A ccumulator A ] INX [ IN crement X ] CPX [ C om P are X ] BNE [ B ranch if N ot E qual] ( is using relative addressing in conjunction with label “LOOP”) LOOP, BNE LOOP, INX, and CPX #$3001 creates a loop. Loop1: Data in accumulator A (#$20) is stored at $2000 + $00 Data in X is incremented #$2000 + #$0001 = #$2001 Data in X is compared to #$3001 Not equal so do another loop Loop2: Data in Accumulator A (#$20) is stored at $2001 Data in X is incremented #$2001 + #$0001 = #$2002 Data in X is compared to #$3001 Not equal so do another loop

ME4447/6405 Why is Indexed Addressing Mode needed?

Example: Store Data Value #$20 into memory locations $2000 to $3000 ORG $1000 LDY #$1001 LDAA #$20 LDX #$2000 LOOP STAA $00,X INX DECY BNE LOOP SWI END The George W. Woodruff School of Mechanical Engineering

ME4447/6405 The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Types of Indexed modes of Addressing Indexed addressing may be implemented in multiple ways. HCS12 CPU uses X, Y, SP or PC as

base index register

for instruction. O

ffset

is then added to

base index register

to form

effective address

.

Constant offset

5-, 9- or 16-bit

signed

offset (-16 to +15, -256 to +255, -32768 to +32767)

5-Bit Constant Offset Indexed Addressing

Index mode uses 5-bit signed offset which is added to base index register (X, Y, SP or PC) to form effective address of memory location that will be affected by instruction. Offset ranges from -16 through +15. Majority of indexed instructions in real programming use offsets that fit in shortest 5-bit form of indexed addressing. Contents of base registers remain unchanged .

LDAA $00, X *load A with (X + $00) The following three statements are equivalent: STAA -8,X Note: offset given in decimal STAA -$08,X STAA $FFF8,X Note: offset given in hex Note: offset given as 16-bit number Let X contain #$3000. After program executed, content of A will be stored at address (#$3000 - #$08) = $2FF8

ME4447/6405 $FFF8 = 1111 1111 1111 1000 0000 0000 0000 0111 1 -------------------------------------------- - 0000 0000 0000 1000 = - #$0008 The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Types of Indexed modes of Addressing

9-Bit Constant Offset Indexed Addressing.

Uses 9-bit signed offset which is added to base index register (X, Y, SP or PC) to form effective address of memory location affected by instruction. Offset ranges from -256 through +255. Contents of base registers are not changed after instruction is executed.

MSB (sign bit) of offset is included in instruction postbyte and remaining 8 bits are provided as extension byte after instruction postbyte in instruction flow. LDAA A6 $FF, X E0 *Assume X contains $1000 prior to instruct. Execut.

FF LDAB E6 -20, Y E9 *Assume Y contains $2000 prior to instruct. Execut.

EC First instruction will load A with value from ($1000 + $FF) = $10FF Second instruction will load B with value from ($2000 – 20) = $IFEC The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Types of Indexed modes of Addressing

Accumulator Offset Indexed Addressing

In this indexed addressing mode, effective address is sum of values in base index register and unsigned offset in one of accumulator. Value in base index register is not changed . Indexed register can be X, Y, SP or PC and accumulator can be either 8-bit (A or B) or 16-bit (D) – A, B, or D accumulator added to

base index register

to form address – Content of accumulator is

unsigned

offset LDAA A6 E5 B, X Instruction adds B to X to form address from which A will be loaded. B and X are not changed by this instruction. The George W. Woodruff School of Mechanical Engineering

ME4447/6405 (Page 21)

Base index register

X Y SP PC rr 00 01 10 11 Example: LDAA B, X Ans: A6 E5 Detailed Explanation: • This is Indexed Addressing Mode with Accumulator Offset.

• Opcode for LDAA is

A6

for this mode.

• From the table above, the formula for postbyte of this mode is: 111rr1aa • rr is 00 because Base Index Register is X • aa is 01 because Accumulator used for offset is B

ME4447/6405 Types of Indexed modes of Addressing - Continued •Auto Pre-/Post-Increment/Decrement •Base index register (X, Y and SP) may be automatically incremented/decremented before or after instruction ( Program Counter may not be used as base register ) •No offset is available •May be incremented/decremented 1 to 8 times Post-Increment (in ranges from 1 through 8): LDX 2,SP+ *Index register X is loaded with contents of (Same as PULX) memory location in stack pointer, then stack EE B1 pointer is incremented twice Pre-Increment (in ranges from 1 through 8): LDX 2,+SP *Stack pointer is incremented twice, EE A1 then Index register X is loaded with contents of memory location in stack pointer Pre-Decrement (in ranges from -8 through -1): STAA 1,-X *Index register X is decremented, then 6A 2F Accumulator A is stored in memory location stored in Index Register X The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Indexed Addressing Mode Postbyte Encoding (xb) The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Indexed Addressing Mode Postbyte Encoding (xb) - Continued The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Why is Pre-/Post-Increment/Decrement Useful?

Example: Store Data Value #$20 into memory locations $2000 to $3000 Without Post-Increment LOOP ORG $1000 LDAA #$20 LDX #$2000 STAA $00,X INX CPX #$3001 BNE LOOP SWI END With Post-Increment LOOP ORG $1000 LDAA #$20 LDX #$2000 STAA 1,X+ CPX #$3001 BNE LOOP SWI END Note: “1” refers to the number of post increments, not an offset!

Program on the Left requires 1 more byte of program memory and takes 1 more cycle to execute per run through the loop than the program on the right. This may make a large difference when the program is large and complex or when dealing with values larger than 16-bits.

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Types of Indexed modes of Addressing - Continued

• 16-Bit Constant Indirect Indexed Addressing – Indexed addressing mode adds 16-bit instruction supplied

offset

to

base indexed register

to form address of memory location that contains pointer to memory location affected by instruction.

– Instruction itself does not point to address of memory location to be acted on.

– Square brackets distinguished this addressing mode from 16-bit constant offset indexing.

Example: LDAA [10, X] or LDAA [$0A, X] The George W. Woodruff School of Mechanical Engineering

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Types of Indexed modes of Addressing - Continued

• 16-Bit Constant Indirect Indexed Addressing ORG $1000 LDAB #$EE *#$EE stored at $0400 STAB LDD STD LDX LDAA …… ......

$0400 #$0400 $5DBC #$5D00 [$BC, X] …… …… *#$0400 stored at $5DBC & $5DBD *X contains #$5D00 *#$BC added to value in X to form address $5DBC. Address pointer $0400 fetched from memory at $5DBC. Value (EE) store in $0400 read & loaded in Acc. A …… SWI END …… The George W. Woodruff School of Mechanical Engineering

ME4447/6405 The George W. Woodruff School of Mechanical Engineering

ME4447/6405 As stated before the Assembler translates an assembly language program into a machine language program Format of machine language program Instruction Address where instruction is located Opcode Postbyte Operand Or Blank if instruction does not use Operands (Note: This format is for Lecture and Tests only !! The real format the assembler outputs is “S19” and will be shown to you in Lab) The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Postbyte and Opcode Reference All Mnemonics and associated Op-codes can be found in Programming Reference Guide pages 6-19 Example: Programming Reference Guide Page 12 (Note: LDAA outlined in red ) The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Indexed Addressing Mode Postbyte Encoding (xb) The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Indexed Addressing Mode Postbyte Encoding (xb) - Continued The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Postbyte Postbyte allows an op-code to be used for more than one instruction.

Determined from Tables 1, 3 or 4 in the programming reference guide Instruction LDAA 0,X LDAA $02,SP+ LDAA B,Y SUBB $1040,X SUBB D,Y SUBB -14,X Opcode A6 A6 A6 E0 E0 E0 Postbyte 00 B1 ED E2 EE 12 Table 1 (Excerpt) The George W. Woodruff School of Mechanical Engineering

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ME4447/6405 The George W. Woodruff School of Mechanical Engineering

ME4447/6405 The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Hand Assembling Example: Assemble the following Program ORG LDAA #$0A LDAB SWI END $1000 #$0B ABA STAA $00 Address $1000 $1002 Opcode Postbyte C6 Operand 86 0A 0B $1004 $1006 $1008 18 3F 06 5A 00 (Note: $1002 since $86 is now at $1000 and $0A is at $1001) The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Example Problem 1 (revisited) ORG LDAB STAB INCB ADDB STAB SWI END $1000 #$0A $1100 $1100 $1090 *Load acc. B with number 0A *Store acc. B in address $1100 *Increment acc. B by 1 *Add memory location $1100 *to acc. B *Store acc. B in address $1090 *Software interrupt The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Hand Assemble Example Problem 1 (Revisited) ORG LDAB #$0A STAB $1100 INCB ADDB $1100 STAB $1090 SWI END $1000 Address Opcode 1000 C6 1002 7B 1005 1006 1009 100B 52 FB 7B 3F Postbyte Operand 0A 1100 1100 1090 The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Example Problem 2 Write a short assembly language program that stores the content of Port T in memory location $3000 after waiting for 0.05 seconds for the input data.

Solution

Recall: One machine cycle = 0.125 x 10 -6 s (8 MHz Bus Clock) We want the HCS12 to wait 0.05 s/0.125 x 10 -6 s = 400,000 cycles One good way to make the HCS12 wait is to create a loop. The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Wait Loop LOOP LDY #$AD9C LDD #$0000 ABA CPX $2000 DEY BNE LOOP 2 cycles 2 cycles 2 cycles 3 cycles 1 cycle 3 cycles Note: These instructions are included to increase the operation time Assume the number of loops needed to wait is 2 bytes (2 + 3 + 1 + 3)*X + 4 = 400,000 cycles X = 44,444 10 = $AD9C The George W. Woodruff School of Mechanical Engineering

ME4447/6405 Example 2 Solution

Solution

*Remember that Port T is input upon reset ORG $1000 LOOP LDY #$AD9C LDD #$0000 ABA *Load Y with 44,444 10 *Clear Accumulator D *Add the contents of B to A CPX $2000 DEY BNE LOOP *Compare X with the contents of *$2000 *Decrement Y *Branch to LOOP if Y is not equal *to zero LDAB $0240 *Load acc. B with content of $0240 STAB $3000 *Store content of acc. B in $3000 SWI *Software Interrupt END The George W. Woodruff School of Mechanical Engineering

ME4447/6405

Homework

Homework 1

•

Write an assembly language program to clear the internal RAM in the MC9S12C32.

•

Write a program to add even/odd numbers located in addresses $0800 through $0900.

Homework 2

•

Write a program to find the largest signed number in a list of numbers stored in address $0A00 through $0BFF. Repeat for an unsigned number.

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ME4447/6405 QUESTIONS???

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