Motorola MC68HC811E2
Microcontrollers
What will be covered within 3
classes
Class 1 Friday March 14th (home work due Tuesday)
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What are Microcontrollers/Microprocessors
Intro into the HC11 chip
Registers, accumulators, Condition Code register, memory
map and other components
Class 2 Monday March 17th
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Motorola Language Code
Data type and symbols
Opcodes, Operands and addressing modes
Class 3 (Tutorial) Tuesday March 18th
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Assembler programming
Assembler Compiling
Assembler Emulating
All done using Oztech Electronics Software
Microprocessors
Microprocessors are components that compute
binary mathematical commands at a specified rate
determined by either an internal or external
oscillating input.
Characterized by:
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Memory addresses registers
Memory data registers
Instruction registers
Index registers
Stack registers
Accumulators
Program counters
Ex: Motorola Microprocessor 6800 (built in the 1980’s)
Microcontrollers
Microcontrollers are microprocessors that
have built in peripherals, such as
communications ports, I/O ports and
others. These devices do not offer
physical access to the address register
and are usually standalone. They offer a
fast and compact control method with
limited physical connections and tools.
What they are used for
Remote monitoring
equipment
Car computer systems
Automating equipment
Cell phones
Computers
Palm Pilots
Singing gift cards
Motorola MC68HC811E2
Microcontroller
HC11
Power saving (stop) and (wait) modes
2048 bytes of EEPROM
256 bytes of RAM
16 bit timer
8-bit pulse accumulator
Real time interrupt circuit
Computer operating properly (COP) watchdog
system
HC11
Synchronous Serial Peripheral Interface (SPI)
Asynchronous Non return to Zero (NRZ) serial
Communication Interface (SCI)
8 channel, 8-bit analogue to digital (A/D)
converters
38 general purpose I/O pins
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16 bidirectional
11 input only, 11 output only
Available in 52pin (PLCC) or 48 pin (DIP)
packages
Internal Structure of the chip
Nomenclature and symboles
Vdd and or Vss mean +5 volts.
GND = ground or 0 volts
PA1 means Port A pin 1
Vrl = voltage reference low
Vrh = voltage reference high
Some pins have more than one function, these
must be setup prior to use. Default is shown in
manual.
Pins with a line above mean “not” or anti”
polar. Thus when 0volts or a “low” is shown at
the reset pin, the chip interprets as a 1 or a
“high”.
Reset pin
All chips have a master reset pin where
a physical reset can occur.
Used for emergencies
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Low power
Frozen
Testing
Startup
Oscillator
All CPUs need an oscillator to jump
between commands.
HC11 is a 4 cycle command chip
Operates at 2Mhz with an 8Mhz cristal
Interrupt Request Queue
There are many different interrupts on
the HC11
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Software IRQ (SIR)
Multitude of input IRQ
 Negative Edge Sensitive
 Positive Edge Sensitive
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Non-maskable IRQ (XIRQ)
 Here nothing can stop the interrupt from
occurring.
 Always an external interrupt pin
Port A
Port A can be configured as:
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Four timer input capture (IC)
Four timer output compare (OC)
Combination of the two
One pulse accumulator (PAI)
General I/O (note directional limits)
Ports
Port B
Port B can be configured for:
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General purpose output pins
Simple Strobed output
Often used for 8-bit data communication
Port C
Port C pins can be configured for:
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General I/O
Used for full handshake modes during
parallel I/O
Often used as multiplexed address/data
signal communication
Port D
Port D pins can be configured for:
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General I/O
Serial Communication Interface (SCI)
Serial Peripheral Interface (SPI)
Port E
Port E pins can be configured for:
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General purpose I/O
Analogue for digital input (A/D)
Note: for high accuracy of A/D, do not read
port E during sampling of A/D, as small
disturbances can reduce the accuracy of
the results.
Chip Layout
CPU Registers
HC11 has five registers and two accumulators
Accumulator D = accA + AccB to form a 16 bit
accumulator
Condition Code Register (CCR)
C = Carry bit, ex: 255+1 = 0 + carry high
V = Overflow ex: 255+1 = 0 and v=1 as the sum has
overflowed capacity
Z = zero bit ex: 1-1 = 0, z=1
N = negative ex: 4-6 = $FD z=1
I = interrupt mask, enables inturrupts
H = half carry (when carry is done from bit 3)
X = X interrupt mask XIRQ (set only by hardware
(XIRQ and Reset pins), cleared only by software)
S = Stop disable (sleep mode mask)
Program Counter
The program counter always points to
the next instruction location to be
executed.
16 bit register
Stack pointer
Stack is usually initialized at the top of
memory and works down
The program is located at the bottom of
memory and works up
If the stack grows too big, it may overwrite
the program, causing a fatal crash
HC11 has 256 bytes of RAM for the stack
16 bit register
Index Registers
HC11 has two index registers
X & Y are 16 bits wide
Used to index memory fetch or storage
of large numbers
Accumulators
Accumulator A is 8 bits long
Accumulator B is 8 bits long
Accumulator D = A + B, where B is the
low byte and A is the high byte.
AccD is used for large number handling
AccA and AccB are the main handlers of
numbers within a program
Memory Map
Memory Map
256 Bytes of RAM at top of memory
address
2K EEPROM from $F800 to $FFFF
64 byte register block is mapped initially
starting from $1000 (this includes
mapped address for ports, pins and
internal configuration setup)
All these can be remapped if needed
End of Day 1
Assignment
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Part1
 Given a input on the lower nibble (4 bit) of PortC,
increment a counter by the input value.
 Display counter output on PortB (8 bit)
 Give a block diagram of events, decision and I/O
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Part2
 Give a block diagram of a delay loop
 Code the delay loop
 Q: Calculate the time it takes to cycle through your delay
loop. Hint: use a nested loop
Example of Block Diagrams
Example 2 of flow diagram
Motorola MC68HC811E2
Microcontrollers
Day 2
Topics that will be covered
Motorola Language Code
Data type and symbols
Opcodes, Operands and addressing
modes
Data types
The default numbering system is decimal in
most compilers
Hexadecimal number are represented by a $
symbol. Ex: $FF = 255 decimal
A number is defined by a# ex1: #45 = 45
decimal. Ex2: #$45 = 69 decimal
Binary number are identified by a b. ex:
#b101010 = #$2A = #42 decimal
Octave numbers are identified by an o ex:
#o10 = #$9 = #9 decimal
Instruction Set (hand out in
class)
Mnemonic = command
Operation = what it does
Description = description of how it does it
Addressing mode = the way it does it
Opcode = machine code that the HC11 sees
Cycles = number of cycles needed to compute
CCR = affected condition code after execution
Addressing modes
There are many ways of executing
commands.
There are six different addressing modes
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Immediate
Direct
Extended
Indexed
Inherent
relative
Immediate
Argument is contained in the byte(s)
immediately following the opcode.
Number of bytes following the opcode
matches the size of the register or
memory location being operated on.
The effective address is the address of
the byte following the instruction
Example of Immediate
Source list:
LDAA #$55 ‘load 55 hex into accA
Object code:
Memory location Memory contents
0100
86
0101
55
Inherent (accumulator/memory)
All information necessary to execute the
instruction is contained in the opcode.
Operations that use only the index
register or accumulators, as well as
control instructions with no arguments,
are included in this addressing mode.
These are one-byte or two-byte
instructions
Example of Inherent
Source list:
PSHA
‘push accA to stack
Object code:
Memory location Memory contents
0100
36
Note: SP = SP -1
Direct addressing mode
The address is found in the next
memory location following the opcode
This enables addressing the first page
of memory (256 bytes)
Execution time is reduced due to less
consumption of space and movement of
bits
Example of direct
Source list:
LDAA $55 ‘load contents from address
$0055 hex into accA
Object code:
Memory location
Memory contents
0100
96
0101
55
…
0055
XX
Note: After insturction, accA = XX
Indexed Addressing Mode
The offset, found in the second memory
location of the instruction, is added to
the contents of the index register to
form a new effective address
The effective address is held in a
temporary address register so that the
contents of the index register are not
changed
Example of Indexed
Source list:
‘X=#$1000
LDAA #$55,X ‘load contents from address
($55 + X) hex into accA
Object code:
Memory location
Memory contents
0100
A6
0101
55
…
1055
YY
Note: After insturction, accA = YY
Extended Addressing mode
Used to address locations in full
memory map
2nd memory location = address high
byte
3rd memory location = address low byte
Example of Extended
Source list:
LDAA $2055 ‘load contents from address
$2055 hex into accA
Object code:
Memory location Memory contents
0100
B6
0101
20
0110
55
…
2055
ZZ
Note: After instruction, accA = ZZ
Relative Addressing Mode
Used for branch type instructions
Program control may be transferred to some
place other than the next sequential memory
location
Transfer is referenced from the next
instruction which the MCU would execute if it
did not transfer control
2 byte instruction
2nd byte contains the offset, which is the
number of memory locations to branch over
Offset is expressed as an 8 bit 2’s compliment
number
Example of Relative
Branch forward example
Source list:
BRA #$20 ‘branch forward 32 +1 positions
Object code:
Memory location
Memory contents
0100
20
0101
20
0110
55
…
100100
RR
100101
DD
Note: After branch, PC = 100110 and executing DD opcode
Note2: Note that opcode for BRA = 20hex, and so is the jump. This
is why a miscalculation of branching can crash your program
Example of Relative
Branch Backwards example
Source list:
BRA #$FE ‘branch backwards 2 - 1 positions
Object code:
Memory location
Memory contents
0010
YY
0011
XX
0100
20
‘BRA #$FE
0101
FE
0110
55
…
100100
RR
100101
DD
Note: After branch, PC = 100 and executing 20 opcode
Note2: Infinit loop
Subroutines
Branch to subroutine
will push the PC onto
the stack
This allows the
program to return to
the program once
the subroutine has
been executed.
F800
BSR SUB
FD00 SUB NOP
FD01
NOP
FD02
RTS
Memory map
00FF 02
00FE F8
Useful Opcodes
ABA
ADDA
ANDA
BCC
BEQ
BITA
BRA
BRSET
CLC
CLI
CLR
CLRA
CMPA
COM
DEC
DECA
DEX
INCA
INS
INX
JSR
LDAA
LSR
NEGA
RTI
RTS
SEC
SEI
STAA
STX
SUBA
SWI
TAB
WAI
Program example1
Example1:
ORG
$0000
LDX
#$0060
LDAA $02
LDAB 2,X
ABA
ORG
FCB
END
$0060
$70,$72,$74,$76
S=1, X=0, I =0
Determine:
accA = _________
accB = _________
PC = ___________
CCR = __________binary
CCR = __________Hex
Program example1
Example1:
ORG
$0000
LDX
#$0060
LDAA $02
LDAB 2,X
ABA
ORG
FCB
END
$0060
$70,$72,$74,$76
accA = $60+ $74 = $D4
accB = $74
PC = $0008
CCR = 1000 1000b
CCR = $88
Program example2
Example2:
ORG
LDS
LDX
LDAA
LDAB
PSHA
PSHB
BSR
NOP
ORG$0F50
PULA
PULB
ABA
RTS
END
$0F00
#$10FF
#$0F00
2,X
#01
SUB1
S=1, X=0, I =0
Determine:
accA=
accB=
PC =
CCR =
SP =
IX =
Does the code work?
Explain.
Program example2
Example2:
ORG
LDS
LDX
LDAA
LDAB
PSHA
PSHB
BSR
NOP
ORG$F850
PULA
PULB
ABA
RTS
END
$F800
#$00FF
#$F800
2,X
#01
SUB1
S=1, X=0, I =0
Determine:
accA= $FF, $F8, $06
accB= $01, $0E
PC = $01FF
CCR = $A1
SP = $01FF
IX = $0F00
00FF
00FE
00FD
00FC
FF
01
0E
F8
The problem is that we
return from the
subroutine to a noncontrolled position.
Program will crash!
Program example3
Example3:
ORG
$F800
SEI
LDX
#$FA00
CLR
1,X
CLR
3,X
LDAA
#$FF
STAA
2,X
CLR
0,X
LDAA
$02
STAA
1,X
STAA
3,X
LDAB
#$FF
STAB
2,X
LDAA
0,X
ABA
END
S=1, X=0, I =0
Determine:
accA=
accB=
PC =
CCR =
IX =
Does the code work?
Explain.
Program example3
Example3:
ORG
$F800
SEI
LDX
#$F8A0
CLR
1,X
CLR
3,X
LDAA
#$FF
STAA
2,X
CLR
0,X
LDAA
$02
STAA
1,X
STAA
3,X
LDAB
#$FF
STAB
2,X
LDAA
0,X
ABA
END
S=1, X=0, I =0
Determine:
accA= $FF, $00, $FF
accB= $FF
PC = $F81C
CCR = $88
IX = $F8A0
FA00
FA01
FA02
FA03
00
00, FA
FF, FF
00, FA
Does the code work?
Explain.
Yes, the code is fully
functioning
Example of Flow Diagram
Assignment Review
Setup code for the Main Program for next
Lab
Setup code for delay loop using nested loops
Your Flow Diagram
Initialize
BSR Delay
Pause
on?
Input PortC
Add Input
with accA
Output accA
To PortB
Delay Loop
Push A &B
Init A & B
DecA
RTS
Pull A & B
A=0?
DecB
B=0?
Assignement2
SUB
CONT
ORG
SEI
LDS
LDAA
CLRB
BSR
ABA
$0000
ORG
INCB
PSHB
DECA
BEQ
BSR
PULB
ABA
RTS
END
$0080
#$0100
#03
SUB
CONT
SUB
INITIALLY: S=1, X=0, I =0
CCR = SXHINZVC
Determine:
accA=
accB=
PC =
SP =
CCR =
What does this program do?