Exam Review

1
Exam Review

• Embedded Programming

2
External Interrupt

• Special Exception
• CPU Saves Status, and PC and Jumps to pre-defined
  address 0x500
• ISR
• Determine what caused the interrupt
• Process it, doing as little as possible
• Restore state of machine
• Return from interrupt
• Fundamental mechanism for multi-tasking

3
Feedback

• Tachometer
• Potentiometer
• Resolver
• Absolute Encoders
• Incremental Encoders
• Phase A
• Phase B
• Index pulse
• Quadrature Decoding
• MPC565 special Feature
• Time Processing Unit
• Parameter Ram
• Host Service Request
• Host Sequence Request
• QDEC function
• Library of interface functions

4
Binary and Hexidecimal Representation of Numbers

• 4 bit 2s compliment
• MSB is sign
• Addition is simple
• 7 0x7 0111b
• 6 0x6 0110b
• 5 0x5 0101b
• 4 0x4 0100b
• 3 0x3 0011b
• 2 0x2 0010b
• 1 0x1 0001b
• 0 0x0 0000b
• -1 0xF 1111b
• -2 0xE 1110b
• -3 0xD 1101b
• -4 0xC 1100b
• -5 0xB 1011b
• -6 0xA 1010b
• -7 0x9 1001b
• -8 0x8 1000b

5
C Coding for Embedded Systems

• Bit wise operations
• Writes and Reads of specific address
• Pointers
• Careful attention to data types
• Understand mapping from data structures into
  memory

6
Operators

• Arithmetic
• ,-,,/, and
• Always result in a number
• Relational
• ,lt,gt,!,gt,and lt
• Always result in true or false (1 or 0)
• Logical
• ,,!
• Treat both sides as true or false, result is true
  or false
• Bitwise
• ,,,,ltlt,gtgt
• Act on bit fields, result is bit fields

7
Setting and Clearing Bits

• Masks
• Register ! MY_BIT_MASK // sets
• Register MY_BIT_MASK // clears Register
  1ltlt6 // sets 7th bit
• Register (1ltlt6) // clears 7th bit
• Structures with bit fields
• MPIO.DDR.B.D0 0 // sets one bit
• MPIO.DDR.B.D0 1 // clears one bit

8
Checking for bit set

• If (MPIO.DR.R 0xFEF)
• // register matches all bits in mask
• If(MPIO.DR.B.D0 0)
• // individual bit is clear

9
Type conversion and casting

• Hard coded numbers must be interpreted by the
  compiler as some data type.
• Int
• 0x12
• 145
• Double
• 12.
• 1.5
• Char
• q

10
Conversion from one type to another will happen

• float a2 // converts int to float
• int b2. // converts double to int
• char c 0xfe // converts int to char
• a 6b/c // does 6b as int
• // converts c to int,
• // does integer division
• // coverts results to a float
• // result will be truncated

11
C preprocessor

• include
• define
• ifdef
• pragma

12
Functions

• Prototypes
• Parameters
• Pass by value
• Pass by pointer
• Return values

13
Writing to a specific memory address

• Pointer
• VUINT32 ptr (VUINT32) 0x12345678
• ptr 15
• Structures