Peripherals

1
Peripherals I/O lines

• All the on-chip peripherals are configured and
  controlled through Special Function Registers
  (SFR)
• Many of the SFRs are bit addressable
• The 111 I/O lines are arranged into Ports
• Some port lines have multiple functions which
  must be configured for correct operation of the
  required function.

2
Infineon 167 I/O Ports

• 111 I/O lines with individual bit addressability
• Tri-stated in input mode
• Selectable input thresholds (not on all pins)
• Push/pull or open drain output mode
• Programmable port driver control

3
M167CS Functional Block Diagram
4
Digital I/O Ports

• Port is where data enters/leaves the system
• Digital I/O lines are normally grouped into 8-bit
  ports or possibly 16-bit ports
• Ports must be configured for input or output
  before they are used
• Most ports allow a mixture of inputs and outputs
  on the same port
• Some microcontrollers have instructions that
  access individual bits of a port

5
M167 digital I/O ports

• Associated with a port is a DIRECTION register
  and on some a Port output control
• Port direction - '0' input, '1' output
• Output control '0' Push/pull, '1'
  open-drain
• In Keil 'C' all the SFR's are defined in the
  header file "c167cs.h" with the Infineon standard
  names
• Px is Port x
• DPx is the Direction for Port x
• ODPx Open Drain Control for Port x

6
Typical Port Structure
7
Output Driver Types
Push/Pull Output Driver
Open-Drain Output Driver
8
Parallel Ports in u-Vision 2
9
Using all bits of ports

• Outputs
• DP4 0xff // Direction all outputs
• P4 value8 // output value to all 8-bits
• DP2 0xffff
• P2 value16
• Inputs
• DP6 0x00 //Direction all inputs
• x P6 // Read all 8-bits into variable x
• x would normally be an unsigned char but could be
  unsigned int

10
Bit Manipulation in 'C'

• 'C' bit operators (binary operators)
• OP symbol Description
• AND
• OR
• XOR
• gtgt n shift bits right n places
• ltlt n shift bits left n places
• y y OP z can be written as y OP z
• E.g.'s y y 0x80 y y gtgt 4 y
  0x80 y gtgt 4
• unary operator complements (invert all bits)
• e.g. y y

11
Masking to achieve bit manipulations

• Masking uses AND and OR operators
• Use OR ('') to set bits to '1'
• Use AND ('') to set bits to 0

OR OR OR
A B Output
0 0 0
0 1 1
1 0 1
1 1 1
AND AND AND
A B Output
0 0 0
0 1 0
1 0 0
1 1 1
XOR XOR XOR
A B Output
0 0 0
0 1 1
1 0 1
1 1 0
12
Controlling output bits Output Masking

• Setting bits to 1 using OR ()
• General format Port Port mask
• Mask has '1' to set a bit, '0' to leave bit
  unchanged.
• Example Set bit 3 to '1'
• P4 P4 0x08 // 0x08 00001000 binary
• Setting bits to 0 using AND ()
• General format Port Port mask
• Mask has '0' to clear a bit, and '1' to leave bit
  unchanged.
• Example Set bit 3 to '0'
• P4 P4 0xf7 // 0xf7 11110111 binary

13
Input Masking

• Use AND () and a mask to isolate a selected bit
• Used in input Polling to test an individual input
  bit
• Loop until a bit becomes logic '1'
• while( (P4 0x08) 0)
• Two possible results 00000000 or 00001000
• I.e. zero or non-zero
• Loop until a bit becomes logic '0'
• while( (P4 0x08) ! 0)
• Often written as while( P4 0x80) // in 'C'
  zero is FALSE, non-zero is TRUE

14
bit variables

• The Keil C compiler supports the bit addressable
  features of Infineon microcontrollers
• General declaration format
• sbit bitname Portxy // port x bit y
• E.g. sbit motor_dir DP210
• sbit motor P210
• MUST declare sbit's before 'C' main() function
• Using sbit's
• motor_dir 1 // Set bit to output
• motor 1 //turn on motor