An integrated circuit that contains many of the same items that a desktop 
computer has, such as CPU, memory, etc., but does not include any “human 
interface” devices like a monitor, keyboard, or mouse. 

Microcontrollers are small (micro) and designed for machine control 
(controller) applications, rather than human interaction.

      WorldWide Microcontroller Shipments (in millions of dollars $) 
          '94     '95      '96      '97      '98      '99      '00 
4-bit  $1,761   1,826    1,849    1,881    1,856    1,816    1,757 
8-bit   4,689   5,634    6,553    7,529    8,423    9,219    9,715 
16-bit    810   1,170    1,628    2,191    2,969    3,678    4,405
 
(2006) A new comprehensive analysis on the Microcontroller market predicts 
that 2007 worldwide microcontroller revenue will increase by 10 percent.           

The fastest growing segment within microcontrollers is the 32-bit market, 
which is estimated to be growing at a compound annual growth rate of 
16 percent each year, compared to the overall market for microcontrollers 
which should garner around 8 percent growth each year on average.

      Average Semiconductor Content per Automobile (in dollars $) 
          '94     '95      '96      '97      '98      '99      '00 
     $  1,068   1,237    1,339    1,410    1,574    1,852    2,126 

(2007)High growth application areas for automotive semiconductors 
include safety (airbags, cruise control, collision avoidance, 
antilock brakes) and cockpit electronics (entertainment, 
telematics, instrumentation, phones).

Electrical and electronics content, including software, represents  
around 20 percent of the cost of the average vehicle. 

A lower-priced vehicle built in 2004 probably has 25 to 30 electronic 
control modules, including 150 to 180 components, while higher-priced 
vehicle might contain 70 control modules with more than 400 components.

Examples:
   controlling traffic lights          CD players
   simple game consoles                many children's games
   TV remote controls                  microwave oven timers
   clock radios                        car engine management systems
   central heating controllers         environmental control systems

 
Get the Microsim software ! 
Register using the Clarion University school code (ask me for ID#)

Read the documentation - it is VERY good...

The simulator consists of:
   HW
      CPU - can alter speed
      256 bytes of random access memory (RAM)
      VDU 64 bytes of output : C0 thru FF
      Seven IO ports (00 thru 06) used  for simulated peripherals  
      Four  8-bit user registers: al, bl, cl, dl
      Three special registers: ip, sp (stack), sr (status)
      On Interrupt (02) triggered by a hardware timer (simulated)
   An assembler
   Ability to single step through or continuously run programs.
   On-line help



In real life,RAM would be replaced by ROM and the system would run 
one program hard wired into the ROM. 



I/O Port Numbers:    
 00 – real keyboard      01 - lift               02 - seven seg
 03 - heater/thermostat  04 - maze               05 - stepper motor       
 06 - lift               07 – virtual keyboard   08 - keypad    


   RAM Addresses: 
   00 - FF
   =======
   00 - BF => used for program & data storage
   C0 - FF => 64 bytes for VDU (4 rows x 16 chars)
              C0 is upper left char, C1 is next char, etc… 

 
Can use register to output binary codes that will control 
the device associated with that I/O port.   
==========================================================   

7 segment display - Uses port2 (Out 2)
Outputs whatever is in al register

1 in lo bit activates right, 0 in lo bit activates left

This will light up left display - all segments
   mov  al, FE
   out  02

This will light up right display - 3 segments
   mov  al, A3
   out  02

Controlling the peripheral devices

The LIFT (elevator) is controlled via I/O port 6.

Code that controls a lift:
=========================
   mov   al,0 
   out   06    ; clear device register
loop:
   in 06       ; Test for lift at top
   push  al    ; done ‘cause you can’t mov bl,al
   pop   bl    ; bl now has what was in al

  ; now create a mask and test 
   and   bl,5  ; Test for MotorUp & TopSwitch
   cmp   bl,5 
   jz StopTop

   in 06       ; Test lift at bottom
   push  al
   pop   bl
   and   bl,A  ; Test for MotorDown AND BottomSwitch
   cmp   bl,A
   jz StopBot

   push  al
   pop   bl
   and   bl,10 ; test for the Call Down button
   jnz   CallDown

   push  al
   pop   bl
   and   bl,20 ; test for the Call Up button
   jnz   CallUp

   jmp   loop

 
Interrupts
==========
When a hardware component (ex: a peripheral device) needs CPU attention, 
the controller associated with this component:
   1. sends Interrupt Request (INTR) signal to the CPU
   2. puts Interrupt Number (0 to FFh) on data bus
   
CPU uses interrupt number to index into interrupt vector table (IVT) 
   Each entry of this table is called an interrupt vector
   Each entry contains address of Interrupt Handler (ISR) 
   CPU transfers control to the corresponding ISR
   Interrupt returns with an IRET



microsim:
      STI turns on HW interrupts
      Interrupt is always INT 02 (only 1 interrupt)
      Vectors to address 2
      MUST have an address of an interrupt routine at address 2
      Use ORG to put routine at a particular address
      Inside the interrupt handler
         save registers (push)
         save flags (pushf)
         process
         restore flags (popf)
         restore registers (pop)
         IRET from interrupt

EXAMPLE
=======
   Jmp   Start ; jump over vector
   DB	40       ; address of isr
Start:
   STI         ; turn on interrupts
   Rep:
   ;
   ; regular code goes here
   ;
   JMP   Rep

   ORG   40    ;  int 02
   ;
   ; interrupt code goes here
   ;
   IRET
END

; An example of using hardware interrupts.
; This program spins the stepper motor continuously and 
; steps the traffic lights on each hardware interrupt.
; WHAT HAPPENS WHEN CLOCK IS   ... S L O W ???
; --------------------------------------------------------------
   JMP   Start    ; Jump past table of interrupt vectors
   DB 50          ; Vector at 02 pointing to address 50
Start:
   STI            ; Set I flag. Enable hardware interrupts
   MOV   AL, 11   ; 11 hex = 00010001b
Rep:
   OUT   05    ; Stepper motor 
   ROR   AL    ; Rotate bits in AL right 00010001,10001000,01000100
   JMP   Rep
 ;-----------------------------------

   ; --- INT 02
        ORG	50
   push	al	; Save AL onto the stack.
	push	bl	; Save BL onto the stack.
	pushf		; Save flags onto the stack.
	MOV	AL, 84	; Red     Green
	OUT	01	; Send AL data to traffic lights
	MOV	AL, 30	; Green Red
	OUT	01	; Send AL data to traffic lights
	popf		; Restore flags to their previous value
	pop	bl	; Restore BL to its previous value
	pop	al	; Restore AL to its previous value
	IRET
	END