DM164120-2 Microchip Technology, DM164120-2 Datasheet - Page 34

• Manufacturer Part Number: DM164120-2
• Description: BOARD DEMO PICKIT 2 44PIN
• Manufacturer: Microchip Technology
• Type: MCUr

Specifications of DM164120-2

• Contents: 3 Boards (1 Populated, 2 Bare)
• Processor To Be Evaluated: PIC16F
• Silicon Manufacturer: Microchip
• Kit Contents: PIC16F Device, 2 PCB Boards
• Features: Small Surface Mount Prototype Area, Two Bare PCB Boards
• Development Tool Type: Hardware - Daughter Card
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: PIC16F887
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

44-Pin Demo Board User’s Guide
DS41296B-page 30
FIGURE 3-10:
3.2.11
The FSR (File Select Register) allows a file register address to be specified. A subse-
quent read or write to the INDF (Indirect File register) refers to the file register
addressed by the FSR.
This may be used to implement a moving average filter. The moving average keeps a
list of the last n values and averages them together. The Filter needs two parts: A
circular queue and a function to calculate the average.
FIGURE 3-11:
Calculating averages in a mid-range PIC microcontroller is best accomplished by using
the FSR to keep track of where the next value will be inserted. This ensures the oldest
value is always overwritten with the newest and doesn’t waste time moving values
within the memory.
Conceptual View
Implementation View
Time
Time
n + 1
n + 2
n + 1
n + 2
Newest value inserted here
n
n
Lesson 11: Indirect Data Addressing
105
106
107
106
106
110
The rest move down one
Before
SWAPF INSTRUCTION
MOVING AVERAGES
After
102
105
106
105
105
110
Pointer to oldest value
101
102
105
101
102
103
Older value overwritten, pointer advanced
1 0 1 0
0 0 1 1
104
101
102
104
101
Pointer advanced
99
104
101
99
99
99
99
0 0 1 1
1 0 1 0
103
104
101
101
101
99
© 2007 Microchip Technology Inc.
105
103
102
102
102
99
107
105
103
105
105
105
Average
Average
103
103
104
103
103
104