Download lecture20

68HC11 Programming
Model & Addressing
Modes
Notes: Tests will be returned in your studios. Grades will be
up by tonight.
Today:
• First Hour: HC11 Programming model
– Section 1.1-1.5 of Huang’s Textbook
– In-class Activity #1
• Second Hour: Addressing Modes
• Section 1.6-1.7 of Huang’s Textbook
– In-class Activity #2
1
Recap: Toy CPU
Address Bus
Memory
Address
Bus
M
A
R
Result Bus
A
P
C
I
R
A
C
B
M
B
R
Memory
Data Bus
Memory Bus
What does a
chip designer
need to know
build the
computer?
Hardware Model
Architecture, hardware timing
specs, electrical specs, wiring
specs, power specs...
2
Programming
• “Program” is the sequence of instructions which
serves as input to the control FSM of the
computer.
• “Machine instruction” is a sequence of binary
digits which can be executed by the processor
• “Assembly language” : assembly instructions
– An assembly instruction is a mnemonic
representation of a machine instruction
– Assembly programs must be translated before
it can be executed: translated by an assembler
• “High-level language”: syntax similar to English
– A translator is required to translate the
program written in a high-level language to
machine language: compiler
3
Toy Programmer’s View
AC (16 bits)
PC (14 bits)
Memory
List of
(16 bits wide,
Instructions
14-bit address)
What does a
programmer
need to know to
program the
computer?
Programming Model
1.
2.
3.
Memory Model
Registers
Instruction Set
Registers such as MAR and MBR are “invisible” to the programmer
4
Toy Instructions
Registers
Mnemonic
Operation
Op-code
LOAD
mem<qhhh> -> AC
00
STORE
AC -> mem<qhhh>
01
ADD
AC + mem<qhhh> -> AC
10
BRN
IF AC<15> =1 THEN qhhh -> PC
11
What
registers
do we
need?
15
AC
13
PC
0
16-bit Accumulator
0
14-bit Program Counter
5
Programming Model
Instruction Format
16-bit Instruction
How many bits are
needed for the
OpCode?
OP
OPERAND
2
How many bits are
needed to access
any memory
location?
14
2-bit OpCode
14-bit Operand
6
Toy Programming Model
Instruction Set
Mnemonic
Operation
Op-code
LOAD
mem<qhhh> -> AC
00
STORE
AC -> mem<qhhh>
01
ADD
AC + mem<qhhh> -> AC
10
BRN
IF AC<15> =1 THEN qhhh -> PC
11
Address Bus
Memory
Address
Bus
M
A
R
P
C
What
bus do
we take?
I
R
7
Introducing the M6811
A “single-chip 8-bit micro-controller”
– Intended to control appliances
– 8-bit data bus
– 16-bit address bus
– Integrates many items on one chip:
» Clock
» CPU
» RAM
» ROM
» Ports for External Input/Output
» Several built-in Input/Output devices like
timers, serial and parallel communication
8
M6811 Hardware Model
PULSE ACCUMULATOR
O
C
1
RAM-256 bytes
PERIODIC INTERRUPT
EEPROM-512 bytes
COP WATCHDOG
PE7
PE6
PE5
PE4
PE3
PE2
PE1
PE0
SPI
PORT
E
A/D
CONVERTER
PORT
A
PORT
D
PA7
PA6
PA5
PA4
PA3
PA2
PA1
PA0
PD5
PD4
PD3
PD2
PD1
RxD
PD0
M68HC11 CPU
RESET
ADDRESS DATA BUS
INTERRUPTS
IRQ
HANDSHAKE I/O
(V PPBULK)
DATA DIRECTION C
XTAL
EXTAL
SS
SCK
MOSI
MISO
TxD
SCI
VREFH
VREFL
XIRQ
PAI
OC2
OC3
OC4
OC5
IC1
IC2
IC3
DATA DIRECTION
ROM-8KB
OSCILLATOR
PORT B
PARALLEL
I/O
PORT C
E
MODA
LIR
MODB
(VSTBY )
VDD
VSS
MODE
SELECT
P P P P P P P P P P P P P P P P S
B B B B B B B B C C C C C C C C T
7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0 R
B
POWER
AA AA AA AA A A AA AA AA
1 1 1 1 1 1 9 8 D D DD DD DD
5 4 3 2 1 0
7 6 5 4 3 2 1 0
S
T
R
A
R/W AS
SINGLE
CHIP
EXPAND
9
M6811 ALU
Bus #1
Memory
Address
Bus
M
A
R
P
C
A
Register File
(A, B, IX, IY,
IR)
MUX
B
F
L
A
G
S
M
B
R
Memory
Data Bus
Bus #2
10
M6811 Memory Model
Memory = 64K x 8
$0000
$hhhh
7 mem
0
Number Notation
$ denotes hexadecimal
h = 0000 .. 1111
$FFFF
15
PC
0
16-bit Program Counter
7 ACCx 0
8-bit Accumulator
11
M6811 Registers
7
A
0
7
B
0
8-bit Accumulators A & B
15
D
0
16-bit Accumulator D
15
IX
0
16-bit Index Register IX
15
IY
0
16-bit Index Register IY
15
PC
0
Program Counter
- - H - N Z V C
Condition Code Register
Carry/borrow (MSB)
oVerflow (2s C)
Zero
Negative
Half carry (bit 34),(BCD)
12
M6811 Instruction Notation
See PRG entry for “LDAA”
LDAA (opr) : opr = data in memory
The Load Accumulator A instruction copies the
contents of the addressed memory register
into the accumulator
This means the contents of memory (M)
replaces the contents of accumulator A (A)
denoted by (M)  (A)
Motorola short-hand notation: M  A
13
Sample Instruction
LDAA
$C120
B6
$C121
C2
$C122
10
$C123
..
LDAA
Transfer content of M($C210) to
Accumulator A
Instruction Format
$C210
12
The instruction
directly
specifies the
address
OPCODE
Address-High Byte
Address-Low Byte
14
Example: LDAA
Memory Segment
$C120
B6
$C121
C2
$C122
10
$C123
..
M6811 Registers
C1
LDAA
IR
23
45
$C210
12
20
PC holds address
PC of next instruction
A
B
A & B contain
values from
previous write
operations
15
1. Fetch Opcode
LDAA Example
Memory Segment
$C120
B6
$C121
C2
$C122
10
$C123
..
$C210
M6811 Registers
C1
20
21
Increment
PC
PC
LDAA
B6
IR
23
A
45
B
12
16
2. Decode Opcode
LDAA Example
Memory Segment
$C120
B6
$C121
C2
$C122
10
$C123
..
$C210
12
M6811 Registers
C1
21
PC
LDAA
B6
IR
23
A
45
B
Decode opcode
How many operand bytes?
(Use PRG)
2
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3. Operand Fetch
LDAA Example
Memory Segment
$C120
B6
$C121
C2
$C122
10
$C123
..
$C210
M6811 Registers
C1
22
21
23
PC
B6
C2
10
23
A
45
B
Increment
PC
LDAA
IR
12
Fetch two operand bytes
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4. Instruction Execution
LDAA Example
Memory Segment
$C120
B6
$C121
C2
$C122
10
$C123
..
$C210
M6811 Registers
C1
23
PC
B6
C2
10
12
23
A
45
B
LDAA
IR
Get data from
memory
12
19
Do Activity #1 Now
It is really, really important to bring
the Huang textbook, and
the 6811 manual
To each and every class
20
HC11 Sample Instructions
The LOAD instructions
A group of instructions that place a value or copy the contents of a
memorylocation (or locations) into a register
LDAA
<opr>
LDAB
<opr>
LDD <opr>
LDX <opr>
LDY <opr>
LDS <opr>
<opr> can be immediate, direct, extended, or index mode
Examples
LDAA
$10
LDX #$1000
21
The ADD instruction
A group of instructions perform addition operation
ABA
ABX
ABY
ADDA <opr>
ADDB <opr>
ADDD <opr>
ADCA <opr>
ADCB <opr>
<opr> is specified using an addressing mode
Examples.
ADDA #10
ADDA $20
ADDD $30
22
The SUB instruction
A group of instructions that perform the subtract operation
SBA
SUBA
SUBB
SUBD
SBCA
SBCB
<opr>
<opr>
<opr>
<opr> ; A  [A] - <opr> - C flag
<opr> ; A  [B] - <opr> - C flag
<opr> can be one of selected addressing modes
Examples
SUBA
SUBA
SUBA
SUBD
#10
$10
0,X
10,X
23
The STORE instruction
A group of instructions that store the contents of a register into
a memory location or memory locations
STAA
STAB
STD
STX
STY
STS
<addr>
<addr>
<addr>
<addr>
<addr>
<addr>
<addr> can be one of selected mode
Examples:
STAA
STAA
STD
STD
STD
$20
10,X
$10
$1000
0,X
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Sample Instruction
How did we specify the operand?
$C120
B6
$C121
C2
$C122
10
$C123
..
LDAA
Transfer content of M($C210) to
Accumulator A
Instruction Format
$C210
12
The instruction
directly
specifies the
address
OPCODE
Address-High Byte
Address-Low Byte
This is not the only way to the job
25
Addressing Modes
5 different ways to specify the operand!
Source
Form
LDAA
Operation
Load Accumulator A
Each way is called an
Addressing Mode
Addressing
Machine Code
Boolean Mode for
Expression Operand Opcode Operand Bytes
MA
IMM
86
ii
2
DIR
96
dd
2
EXT
B6
hh ll
3
IND,X
A6
ff
2
IND,Y
18 A6
ff
3
They have different
OpCodes
How do we tell these addressing modes apart?
26
Address Mode Examples
Source
Form
LDAA
Operation
Load Accumulator A
Addressing
Machine Code
Boolean Mode for
Expression Operand Opcode Operand Bytes
MA
IMM (immediate)
86 28 : LDAA #$28
Load ACCA with the "immediate"
constant $28
DIR (direct)
96 28 : LDAA $28
Load ACCA with the content of memory
address $0028
IMM
86
ii
2
DIR
96
dd
2
EXT
B6
hh ll
3
IND,X
A6
ff
2
IND,Y
18 A6
ff
3
How much of the address space
can we "reach" with DIR?
256 Bytes
What is this mode good for?
Saves Bytes & Fetches
27
Address Mode Examples-2
Source
Form
LDAA
Operation
Load Accumulator A
Addressing
Machine Code
Boolean Mode for
Expression Operand Opcode Operand Bytes
MA
EXT (extended)
B6 C128 : LDAA $C128
Load ACCA with the content of memory
address $C128
IMM
86
ii
2
DIR
96
dd
2
EXT
B6
hh ll
3
IND,X
A6
ff
2
IND,Y
18 A6
ff
3
How much of the address space
can we "reach" with EXT?
65536 Bytes
What is this mode good for?
Reaches all memory
28
Address Mode Examples-3
Source
Form
LDAA
Operation
Load Accumulator A
Addressing
Machine Code
Boolean Mode for
Expression Operand Opcode Operand Bytes
MA
IND,X (indexed,X)
A6 28: LDAA $28,X
Load ACCA with the content of memory
address (EA), where
EA = IX + $28
IX is called an Index Register
It holds a 16-bit base address
The operand is an unsigned offset byte
EA = Base + Offset
There’s another index register, IY
IMM
86
ii
2
DIR
96
dd
2
EXT
B6
hh ll
3
IND,X
A6
ff
2
IND,Y
18 A6
ff
3
How much of the address space
can we "reach" with IND,X?
256 Bytes
What is this mode good for?
Addressing elements in an array
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What’s the big idea?
All of the addressing modes were developed in response to specific needs
Need
Addressing Mode
Reach the first 256 RAM
locations quickly
Direct
Load a constant without having
to first put it in memory
Immediate
Access arrays of numbers
efficiently, implement pointers
Indexed
We’ll do array and pointer examples later...
30
Address Mode Summary
Immediate
OP CODE
DATA
OP CODE
DATA-High
16-bit data
DATA-Low
Direct
OP CODE
00
Address-Low
Address-Low
Extended
OP CODE
Address-High
Address-Low
Address-High Address-Low
Effective Address
Indexed
OP CODE
Offset
Address-High Address-Low
Index Register
31
Do Activity #2 Now
Due: End of Class Today.
RETAIN THE LAST PAGE(S) (#3 onwards)!!
For Next Class:
• Bring Huang Textbook, & HC11 PRG
• Required Reading:
– Sec 2.1-2.4, 2.8 of Huang
• This reading is necessary for getting points in
the Studio Activity!
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