2. Physics 413 Chapter 1: Introduction to the HCS 12 Microcontroller

3. Computer Architecture What is a Digital Computer ? A computer is essentially a fast electronic calculating machine. What is a program ? A program is a set of very simple instructions that a computer can understand. Examples of simple instructions are ADD two numbers, Is X > Y?, COPY A into the memory. What is Machine Language ? The set of exceedingly simple and primitive instructions that a computer can understand is called the Instruction Set or Machine Language.

4. Architecture and Organization Computer Architecture deals with the design of those components of a computer that are accessible to a programmer. For instance, the Motorola 6800 does not have a MUL instruction but the Pentium does. Computer Organization deals with the implementation of the architecture and may be transparent to the programmer. For instance, precisely how is MUL implemented in the hardware?

5. Levels of Abstraction L5 High ‑ level Language (C++, Java) L4 Assembly Language L3 Operating System L2 Instruction Set Architecture (ISA) L1 Microarchitecture Level L0 Digital Logic Level Transistors

6. A Brief History of Computers First Generation ‑ Vacuum Tubes ‑ 1945 ‑ 1955 ENIAC (Electronic Numerical Integrator and Computer) had 18,000 Vacuum Tubes, 1500 relays and weighed 30 tons Second Generation ‑ Transistors ‑ 1955 ‑ 65 ‑ PDP ‑ 8 (DEC) Third Generation ‑ IC ‑ 1965 ‑ 80 ‑ IBM 360 Fourth Generation ‑ VLSI ‑ Intel and AMD Processors

7. Moore’s Law The number of transistors on a chip doubles every 18 months

8. All about microprocessors and microcontrollers ROM is where the program that initializes the PC is stored. RAM access is fast ADDRESS BUS carries the address of RAM, ROM, and other peripherals HCS12 has 16 multiplexed address and data lines DATA BUS carries data back and forth between the microprocessor and RAM, ROM, and other peripherals.

9. Memory Big Endian: 4 bytes arranged as:0123 (32 ‑ bit word) Little Endian: 4 bytes arranged 3210 (32 ‑ bit word) DRAM Organization nxn matrix structure is popular for large memory sizes RAS ‑ Row Address Strobe CAS ‑ Column Address Strobe RAS ‑ CAS strategy reduces the number of pins but slows down access because two addressing cycles are required SRAM Fast for cache

10. ROM PROM EPROM ‑ UV erasable EEPROM ‑ Electrically erasable byte at a time FLASH ‑ electrical block erasable ‑ digital film ‑ more like RAM!

11. HCS12 Data Sheet http://www.freescale.com/files/microcontrollers/doc/data_sheet/H CS12DFAMILYPP.pdf

12. HCS12 Architecture X BA CCR PC SP A + B = D Y

13. Straight-line Programming In Paris they simply stared when I spoke to them in French ; I never did succeed in making those idiots understand their own language Mark Twain, The Innocents Abroad, 1869

14. My First Program  CLRA Clears accumulator A ( A = 0 )  INC A This instruction does this: A + 1 A  SWI Stop (software interrupt)

15. Op-codes Assembly Language Memory Location Op-codes CLRA 2000 87 INCA 2001 42 SWI 2002 3F

16. My Second Program LDAA # $ 12 ADDA # $ 15 SWI

17. Object Code... Program # 2 Assembly Language Memory Location Op-codes LDAA # $ 12200086 200112 ADDA # $ 1520028B 200315 SWI 20043F

18. Addressing Modes  Inherent (implied) : Simplest with no operand. One-byte op-code. Examples: INCA and CLRA  Immediate : Operand specified is immediate (no memory access). Examples: LDAA # $ 12 and ADDA # $ 15

19. Immediate and Direct Modes  Immediate LDAA # $ 12 Load the hex number 12  op-code 86 12  Direct LDAA $ 12 Load from memory location 0012  op-code 96 12

20. My Third Program Assembly Language Memory Location Op-codes LDAA # $ 04 STAA $ 15 LDAA # $ 08? ? ADDA $ 15 SWI

21. My Third Program Assembly Language Memory Location Op-codes LDAA # $ 04200086 04 STAA $ 15 200297 15 LDAA # $ 08200486 08 ADDA $ 1520069B 15 SWI 20083F

22. Extended Addressing Mode  The extended addressing mode becomes indispensable when memory locations beyond the zero page must be addressed. [This is the case for the HCS12 on the Dragon12 Board in the lab]  Here, as always, an example is worth a thousand words:  LDAA $3C5E Load A from memory location 3C5E  Op-codes B6 3C 5E

23. Three Trick Questions  What is the outcome of B6 00 2A ?  What is the outcome of LDAA # $ 3C5E ?  What is the outcome of STAB $3C44 ?

24. Trick Questions... Answered!  What is the outcome of B6 00 2A ? Legal but not very smart.  What is the outcome of LDAA # $ 3C5E ? Not Legal  What is the outcome of STAB $3C44 ? O.K. and op-code is F7 3C 44

25. Index Register X is a 16-bit register How are the following three instructions different? LDX # $ 5C42 LDX $ 5C42 LDX $ 5C

26. Index Register  LDX #$ 5C42 The number 5C42 is loaded into X  LDX $ 5C42 Numbers from 5C43 and 5C42 loaded  LDX $ 5C Numbers from 005D and 005C loaded

27. Indexed Addressing Mode LDAA 0,X loads accumulator A with the contents of the memory location pointed to by the index register X. LDAA 4,X loads accumulator A with the contents of the memory location pointed to by X+4

28. Transfer and Exchange!  TFR D,X transfers the contents of D to X  TFR X, B transfers bits 0-7 of X to B  EXG A,B swaps A and B

29. Move it!  Memory to memory transfer  movb $1000,$2000 copies the (8-bit)contents of memory location $1000 to the memory location $2000  movw 0,X,0,Y copies the 16-bit word pointed to by X to the memory location pointed to by Y.

30. Examples Galore  ADDA The outcome is A + M A  ADDA # $ 2B8B 2B  ADDA $ 3C9B 3C  ADDA $ 5B24 AB 5B 24

31. Carry Bit in CCR  ADCA The outcome is A + M + C A  Use this instruction when expecting a carry. Incidentally, CLC will clear the carry bit.

32. Indexed Addressing Mode LDX # $ 0050 LDAA 0,X ADDA 1,X SWI Program adds two numbers stored in memory locations 0050 and 0051

33. D-bug12 Assembler ASM 2000 Begin assembly at address 2000 End Assembly LOAD Load S-Records into memory MD Memory Display MM Modify Memory RD Display CPU registers RM Modify CPU Register Contents PC 2000 loads 2000 into PC T Trace (single-step)