8-pin Flash PIC® Microcontroller Tips ‘n Tricks CHAPTER 1 8-Pin Flash PIC® Microcontrollers Tips ‘n Tricks Table Of Contents TIPS ‘N TRICKS WITH HARDWARE TIP #1: Dual Speed RC Oscillator ................ 1-2 TIP #2: Input/Output Multiplexing.................. 1-2 TIP #3: Read Three States From One Pin .... 1-3 TIP #4: Reading DIP Switches...................... 1-3 TIP #5: Scanning Many Keys With One Input.......................................... 1-4 TIP #6: Scanning Many Keys and Wake-up From Sleep ....................................... 1-4 TIP #7: 8x8 Keyboard with 1 Input ................ 1-5 TIP #8: One Pin Power/Data......................... 1-5 TIP #9: Decode Keys and ID Settings .......... 1-6 TIP #10: Generating High Voltages ................ 1-6 TIP #11: VDD Self Starting Circuit.................... 1-7 TIP #12: Using PIC® MCU A/D For Smart Current Limiter.................................. 1-7 TIP #13: Reading A Sensor With Higher Accuracy........................................... 1-8 TIP #13.1: Reading A Sensor With Higher Accuracy – RC Timing Method ......... 1-8 TIP #13.2: Reading A Sensor With Higher Accuracy – Charge Balancing Method ............................................. 1-10 TIP #13.3: Reading A Sensor With Higher Accuracy – A/D Method .................... 1-11 TIP #14: Delta Sigma Converter ..................... 1-11 TIPS ‘N TRICKS WITH SOFTWARE TIP #15: Delay Techniques ............................. 1-12 TIP #16: Optimizing Destinations.................... 1-13 TIP #17: Conditional Bit Set/Clear .................. 1-13 TIP #18: Swap File Register with W ............... 1-14 TIP #19: Bit Shifting Using Carry Bit ............... 1-14 © 2008 Microchip Technology Inc. TIPS ‘N TRICKS INTRODUCTION Microchip continues to provide innovative products that are smaller, faster, easier to use and more reliable. The 8-pin Flash PIC® microcontrollers (MCU) are used in an wide range of everyday products, from toothbrushes, hair dryers and rice cookers to industrial, automotive and medical products. The PIC12F629/675 MCUs merge all the advantages of the PIC MCU architecture and the flexibility of Flash program memory into an 8-pin package. They provide the features and intelligence not previously available due to cost and board space limitations. Features include a 14-bit instruction set, small footprint package, a wide operating voltage of 2.0 to 5.5 volts, an internal programmable 4 MHz oscillator, on-board EEPROM data memory, on-chip voltage reference and up to 4 channels of 10-bit A/D. The flexibility of Flash and an excellent development tool suite, including a low-cost In-Circuit Debugger, In-Circuit Serial Programming™ and MPLAB® ICE 2000 emulation, make these devices ideal for just about any embedded control application. TIPS ‘N TRICKS WITH HARDWARE The following series of Tips ’n Tricks can be applied to a variety of applications to help make the most of the 8-pin dynamics. Page 1-1 8-pin Flash PIC® Microcontroller Tips ‘n Tricks TIP #1 Dual Speed RC Oscillator TIP #2 Input/Output Multiplexing Figure 1-1 Individual diodes and some combination of diodes can be enabled by driving I/Os high and low or switching to inputs (Z). The number of diodes (D) that can be controlled depends on the number of I/Os (GP) used. +5V R1 PIC12F6XX R2 GP0 OSC1 C The equation is: D = GP x (GP - 1). Example 2-1: Six LEDs on Three I/O Pins 1. After reset I/O pin is High-Z 2. Output ‘1’ on I/O pin 3. R1, R2 and C determine OSC frequency 4. Also works with additional capacitors Frequency of PIC MCU in external RC oscillator mode depends on resistance and capacitance on OSC1 pin. Resistance is changed by the output voltage on GP0. GP0 output ‘1’ puts R2 in parallel with R1 reduces OSC1 resistance and increases OSC1 frequency. GP0 as an input increases the OSC1 resistance by minimizing current flow through R2, and decreases frequency and power consumption. Page 1-2 LEDs 1 2 3 4 5 6 0 0 1 Z Z 0 1 0 0 0 1 1 1 1 0 1 0 0 0 0 0 0 1 1 0 0 0 0 0 1 0 0 1 Z Z 0 1 1 0 0 1 1 0 Z Z 1 0 1 0 1 0 1 0 1 0 1 0 0 1 0 0 0 0 0 0 0 1 1 0 0 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 0 0 0 1 0 1 0 1 0 0 0 0 0 0 0 0 0 0 1 0 0 0 1 0 1 0 Figure 2-1 PIC12F6XX GP0 Summary: GP0 = Input: Slow speed for low current GP0 = Output high: High speed for fast processing GPx 0 1 2 GP1 GP2 2 1 3 5 6 4 © 2008 Microchip Technology Inc. 8-pin Flash PIC® Microcontroller Tips ‘n Tricks TIP #3 Read Three States From One Pin To check state Z: Figure 3-1 • Drive output pin high • Set to Input • Read 1 PIC • Drive output pin low I/O • Set to Input • Read 0 TIP #4 Reading DIP Switches 5V Link 1 Link 0 0V To check state 0: • Read 0 on pin To check state 1: • Read 1 on pin State Link 0 Link 1 0 closed open 1 open closed NC open open Jumper has three possible states: not connected, Link 1 and Link 0. The capacitor will charge and discharge depending on the I/O output voltage allowing the “not connected” state. Software should check the “not connected” state first by driving I/O high, reading 1 and driving I/O low and reading 0. The “Link 1” and “Link 0” states are read directly. The input of a timer Example 4-1 can be used to test movlw which switch(s) movwf movwf is closed. The movlw movwf input of Timer1 is movlw held high with a movwf clrf pull-up resistor. LOOP clrf Sequentially, movf each switch I/O is movwf btfsc set to input and andwf bsf Timer1 is checked rlf for an increment btfsc goto indicating the retlw switch is closed. TMR1L Mask,W TRISIO TMR1L,0 DIP,F STATUS,C Mask,F Mask,4 Loop 0 Each bit in the DP register represents its corresponding switch position. By setting Timer1 to FFFFh and enabling its interrupt, an increment will cause a rollover and generate an interrupt. This will simplify the software by eliminating the bit test on the TMR1L register. Sequentially set each GPIO to an input and test for TMR1 increment (or 0 if standard I/O pin is used). Figure 4-1 VDD PIC12F6XX 10K GP5/T1CKI Data I/O © 2008 Microchip Technology Inc. b'11111111' TRISIO DIP b'00000111' T1CON b'11111110' Mask GPIO GP4 GP3 GP2 GP1 GP0 Page 1-3 8-pin Flash PIC® Microcontroller Tips ‘n Tricks TIP #5 Scanning Many Keys With One Input TIP #6 Scanning Many Keys and Wake-up From Sleep The time required to charge a capacitor depends on resistance between VDD and capacitor. When a button is pressed, VDD is supplied to a different point in the resistor ladder. The resistance between VDD and the capacitor is reduced, which reduces the charge time of the capacitor. A timer is used with a comparator or changing digital input to measure the capacitor charge time. The charge time is used to determine which button is pressed. An additional I/O can be added to wake the part when a button is pressed. Prior to Sleep, configure GP1 as an input with interrupt-onchange enabled and GP2 to output high. The pull-down resistor holds GP1 low until a button is pressed. GP1 is then pulled high via GP2 and VDD generating an interrupt. After wake-up, GP2 is configured to output low to discharge the capacitor through the 220Ω resistor. GP1 is set to output high and GP2 is set to an input to measure the capacitor charge time. Software sequence: 1. Configure GP2 to output a low voltage to discharge capacitor through I/O resistor. 2. Configure GP2 as one comparator input and CVr ef as the other. 3. Use a timer to measure when the comparator trips. If the time measured is greater than the maximum allowed time, then repeat; otherwise determine which button is pressed. • GP1 pin connected to key common • Enable wake-up on port change • Set GP1 as input and GP2 high prior to Sleep • If key is pressed the PIC MCU wakes up, GP2 must be set low to discharge capacitor • Set GP1 high upon wake-up to scan keystroke Figure 6-1 When a key is pressed, the voltage divider network changes the RC ramp rate. VDD Figure 5-1 100R R R R R PIC12F6XX GP5 GP0 GP4 GP1 GP3 GP2 16 Resistors R 220Ω R PIC12F6XX GP5 16 Resistors R GP0 GP4 GP1 GP3 GP2 R 220Ω See AN512, “Implementing Ohmmeter/ Temperature Sensor” for code ideas. Page 1-4 © 2008 Microchip Technology Inc. 8-pin Flash PIC® Microcontroller Tips ‘n Tricks TIP #7 4x4 Keyboard with 1 Input TIP #8 One Pin Power/Data By carefully selecting the resistor values, each button generates a unique voltage. This voltage is measured by the A/D to determine which button is pressed. Higher precision resistors should be used to maximize voltage uniqueness. The A/D will read near 0 when no buttons are pressed. A single I/O can be used for both a singledirection communication and the power source for another microcontroller. The I/O line is held high by the pull-up resistor connected to VDD. The sender uses a pull-down transistor to pull the data line low or disables the transistor to allow the pull-up to raise it to send data to the receiver. VDD is supplied to the sender through the data line. The capacitor stabilizes the sender’s VDD and a diode prevents the capacitor from discharging through the I/O line while it is low. Note that the VDD of the sender is a diode-drop lower than the receiver. Figure 7-1 VDD Figure 8-1 PIC12F6XX VDD GP0 Receiver GP0 © 2008 Microchip Technology Inc. VDD VDD - 0.7V Sender GP0 Page 1-5 8-pin Flash PIC® Microcontroller Tips ‘n Tricks TIP #9 Decode Keys and ID Settings TIP #10 Generating High Voltages Buttons and jumpers can share I/O’s by using another I/O to select which one is read. Both buttons and jumpers are tied to a shared pull-down resistor. Therefore, they will read as ‘0’ unless a button is pressed or a jumper is connected. Each input (GP3/2/1/0) shares a jumper and a button. To read the jumper settings, set GP4 to output high and each connected jumper will read as ‘1’ on its assigned I/O or ‘0’ if it’s not connected. With GP4 output low, a pressed button will be read as ‘1’ on its assigned I/O and ‘0’ otherwise. Figure 10-1 Figure 9-1 GP0 GP1 GP2 GP3 GP4 VDD PIC12F6XX w/RC CLKOUT VDD VOUT max = 2 * VDD - 2 * VDIODE CLKOUT CPUMP CFILTER Voltages greater than VDD can be generated using a toggling I/O. PIC MCUs CLKOUT/OSC2 pin toggles at one quarter the frequency of OSC1 when in external RC oscillator mode. When OSC2 is low, the VDD diode is forward biased and conducts current, thereby charging CPUMP. After OSC2 is high, the other diode is forward biased, moving the charge to CFILTER. The result is a charge equal to twice the VDD minus two diode drops. This can be used with a PWM, a toggling I/O or other toggling pin. • When GP4 = 1 and no keys are pressed, read ID setting • When GP4 = 0, read the switch buttons Page 1-6 © 2008 Microchip Technology Inc. 8-pin Flash PIC® Microcontroller Tips ‘n Tricks Building on the previous topic, the same charge pump can be used by the MCU to supply its own VDD. Before the switch is pressed, VBAT has power and the VDD points are connected together but unpowered. When the button is pressed, power is supplied to VDD and the MCUs CLKOUT (in external RC oscillator mode) begins toggle. The voltage generated by the charge pump turns on the FET allowing VDD to remain powered. To power down the MCU, execute a Sleep instruction. This allows the MCU to switch off its power source via software. TIP #12 Using PIC® MCU A/D For Smart Current Limiter Figure 12-1 PIC12F6XX 10K W TIP #11 VDD Self Starting Circuit Load or Motor AN0 RSENSE Advantages: • PIC MCU leakage current nearly 0 • Low cost (uses n-channel FET) • Reliable • No additional I/O pins required • Detect current through low side sense resistor • Optional peak filter capacitor • Varying levels of overcurrent response can be realized in software Figure 11-1 VBAT VDD VDD VDD CLKOUT VDD By adding a resistor (RSENSE) in series with a motor, the A/D can be used to measure in-rush current, provide current limiting, over-current recovery or work as a smart circuit breaker. The 10K resistor limits the analog channel current and does not violate the source impedance limit of the A/D. PIC12F6XX © 2008 Microchip Technology Inc. Page 1-7 8-pin Flash PIC® Microcontroller Tips ‘n Tricks TIP #13 Reading a Sensor With Higher Accuracy Tip #13.1 Reading a Sensor With Higher Accuracy – RC Timing Method Sensors can be read directly with the A/D but in some applications, factors such as temperature, external component accuracy, sensor nonlinearity and/or decreasing battery voltage need to be considered. In other applications, more than 10 bits of accuracy are needed and a slower sensor read is acceptable. The following tips deal with these factors and show how to get the most out of a PIC MCU. RC Timing Method: 13.1. RC Timing Method (with reference resistor) Simple RC step response Vc(t) = VDD * (1 - e -t/(RC)) t = -RC ln(1 - VTH/VDD) VTH/VDD is constant R2 = (t2/t1) * R1 Figure 13-1 Vc(t) 13.2. Charge Balancing Method R1 R2 13.3. A/D Method VTH t=0 t = t1 Time t = t2 A reference resistor can be used to improve the accuracy of an analog sensor reading. In this diagram, the charge time of a resistor/capacitor combination is measured using a timer and a port input or comparator input switches from a ‘0’ to ‘1’. The R1 curve uses a reference resistor and the R2 curve uses the sensor. The charge time of the R1 curve is known and can be used to calibrate the unknown sensor reading, R2. This reduces the affects of temperature, component tolerance and noise while reading the sensor. Page 1-8 © 2008 Microchip Technology Inc. 8-pin Flash PIC® Microcontroller Tips ‘n Tricks Application Notes: AN512, “Implementing Ohmmeter/Temperature Sensor” AN611, “Resistance and Capacitance Meter Using a PIC16C622” Here is the schematic and software flow for using a reference resistor to improve the accuracy of an analog sensor reading. The reference resistor (RREF) and sensor (RSEN) are assigned an I/O and share a common capacitor. GP0 is used to discharge the capacitor and represents the capacitor voltage. Through software, a timer is used to measure when GP0 switches from a ‘0’ to a ‘1’ for the sensor and reference measurements. Any difference measured between the reference measurement and its calibrated measurement is used to adjust the sensor reading, resulting in a more accurate measurement. The comparator and comparator reference on the PIC12F629/675 can be used instead of a port pin for a more accurate measurement. Polypropylene capacitors are very stable and beneficial in this type of application. 1. Set GP1 and GP2 to inputs, and GP0 to a low output to discharge C 2. Set GP0 to an input and GP1 to a high output 3. Measure tRSEN (GP0 changes to 1) 4. Repeat step 1 5. Set GP0 to an input and GP2 to a high output 6. Measure tRREF (GP0 changes to 1) 7. Use film polypropylene capacitor 8. RTH = x RREF tRSEN tRREF Figure 13-2 PIC12F629 RREF GP2 RSEN GP1 GP0 Other alternatives: voltage comparator in the PIC12F6XX to measure capacitor voltage on GP0. © 2008 Microchip Technology Inc. Page 1-9 8-pin Flash PIC® Microcontroller Tips ‘n Tricks Tip #13.2 Reading a Sensor With Higher Accuracy – Charge Balancing Method The comparator and comparator voltage reference (CVREF) on the PIC12F629/675 are ideal for this application. 1. Sensor charges a capacitor 1. GP1 average voltage = CVREF 2. Reference resistor discharges the capacitor 2. Time base as sampling rate 3. Modulate reference resistor to maintain constant average charge in the capacitor 3. At the end of each time base period: - If GP1 > CVREF, then GP2 Output Low - If GP1 < CVREF, then GP2 Input mode 4. Use comparator to determine modulation To improve resolution beyond 10 or 12 bits, a technique called “Charge Balancing” can be used. The basic concept is for the MCU to maintain a constant voltage on a capacitor by either allowing the charge to build through a sensor or discharge through a reference resistor. A timer is used to sample the capacitor voltage on regular intervals until a predetermined number of samples are counted. By counting the number of times the capacitor voltage is over an arbitrary threshold, the sensor voltage is determined. 4. Accumulate the GP2 lows over many samples 5. Number of samples determines resolution 6. Number of GP2 lows determine effective duty cycle of Rr ef Figure 13-3 VDD PIC12F6XX CVREF RSEN + GP1 RREF COUT - T1G GP2 Page 1-10 © 2008 Microchip Technology Inc. 8-pin Flash PIC® Microcontroller Tips ‘n Tricks Tip #13.3 Reading a Sensor With Higher Accuracy – A/D Method NTC (Negative Temperature Coefficient) sensors have a non-linear response to temperature changes. As the temperature drops, the amount the resistance changes becomes less and less. Such sensors have a limited useful range because the resolution becomes smaller than the A/D resolution as the temperature drops. By changing the voltage divider of the RSEN, the temperature range can be expanded. To select the higher temperature range, GP1 outputs ‘1’ and GP2 is set as an input. For the lower range, GP2 outputs ‘1’ and GP1 is configured as an input. The lower range will increase the amount the sensor voltage changes as the temperature drops to allow a larger usable sensor range. TIP #14 Delta-Sigma Converter The charge on the capacitor on GP1 is maintained about equal to the CVREF by the MCU monitoring COUT and switching GP2 from Input mode or output low appropriately. A timer is used to sample the COUT bit on a periodic basis. Each time GP2 is driven low, a counter is incremented. This counter value corresponds to the input voltage. To minimize the affects of external component tolerances, temperature, etc., the circuit can be calibrated. Apply a known voltage to the input and allow the microcontroller to count samples until the expected result is calculated. By taking the same number of samples for subsequent measurements, they become calibrated measurements. Figure 14-1 PIC12F6XX Summary: High range: GP1 output ‘1’ and GP2 input Low range: GP1 input and GP2 output ‘1’ 1. 10K and 100K resistors are used to set the range CVREF VIN GP1 + COUT - 2. Vr ef for A/D = Vdd 3. Rth calculation is independent of Vdd GP2 4. Count = Rsen/(Rsen+Rr ef ) x 255 5. Don’t forget to allow acquisition time for the A/D 1. GP1 average voltage = CVREF Figure 13-4 PIC12F675 100K GP2 2. Time base as sampling rate 3. At the end of each time base period: - If GP1 > CVREF, then GP2 Output Low - If GP1 < CVREF, then GP2 Output High GP1 4. Accumulate the GP2 lows over many samples AN0 (A/D Input) 5. Number of samples determines resolution 10K RSEN © 2008 Microchip Technology Inc. Page 1-11 8-pin Flash PIC® Microcontroller Tips ‘n Tricks TIPS ‘N TRICKS WITH SOFTWARE To reduce costs, designers need to make the most of the available program memory in MCUs. Program memory is typically a large portion of the MCU cost. Optimizing the code helps to avoid buying more memory than needed. Here are some ideas that can help reduce code size. TIP #15 Delay Techniques • Use GOTO “next instruction” instead of two NOPs. • Use CALL Rtrn as quad, 1 instruction NOP (where “Rtrn” is the exit label from existing subroutine). Example 15-1 NOP NOP GOTO Rtrn ;2 instructions, 2 cycles $+1 CALL Rtrn . . . RETURN ;1 instruction, 2 cycles ;1 instruction, 4 cycles MCUs are commonly used to interface with the “outside world” by means of a data bus, LEDs, buttons, latches, etc. Because the MCU runs at a fixed frequency, it will often need delay routines to meet setup/hold times of other devices, pause for a handshake or decrease the data rate for a shared bus. Page 1-12 Longer delays are well-suited for the DECFSZ and INCFSZ instructions where a variable is decremented or incremented until it reaches zero when a conditional jump is executed. For shorter delays of a few cycles, here a few ideas to decrease code size. For a two-cycle delay, it is common to use two NOP instructions which uses two program memory locations. The same result can be achieved by using “goto $+1”. The “$” represents the current program counter value in MPASM™ Assembler. When this instruction is encountered, the MCU will jump to the next memory location. This is what it would have done if two NOP’s were used but since the GOTO instruction uses two instruction cycles to execute, a two-cycle delay was created. This created a two-cycle delay using only one location of program memory. To create a four-cycle delay, add a label to an existing RETURN instruction in the code. In this example, the label “Rtrn” was added to the RETURN of subroutine that already existed somewhere in the code. When executing “CALL Rtrn”, the MCU delays two instruction cycles to execute the CALL and two more to execute the RETURN. Instead of using four NOP instructions to create a four-cycle delay, the same result was achieved by adding a single CALL instruction. © 2008 Microchip Technology Inc. 8-pin Flash PIC® Microcontroller Tips ‘n Tricks TIP #16 Optimizing Destinations TIP #17 Conditional Bit Set/Clear • Destination bit determines W for F for result • Look at data movement and restructure • To move single bit of data from REGA to REGB • Precondition REGB bit • Test REGA bit and fix REGB if necessary Example 16-1 Example: A + B → A MOVF ADDWF MOVWF A,W B,W A 3 instructions MOVF ADDWF Example 17-1 B,W A,F 2 instructions Careful use of the destination bits in instructions can save program memory. Here, register A and register B are summed and the result is put into the A register. A destination option is available for logic and arithmetic operations. In the first example, the result of the ADDWF instruction is placed in the working register. A MOVWF instruction is used to move the result from the working register to register A. In the second example, the ADDWF instruction uses the destination bit to place the result into the A register, saving an instruction. BTFSS BCF BTFSC BSF REGA,2 REGB,5 REGA,2 REGB,5 4 instructions BCF REGB,5 BTFSC REGA,2 BSF REGB,5 3 instructions One technique for moving one bit from the REGA register to REGB is to perform bit tests. In the first example, the bit in REGA is tested using a BTFSS instruction. If the bit is clear, the BCF instruction is executed and clears the REGB bit, and if the bit is set, the instruction is skipped.The second bit test determines if the bit is set, and if so, will execute the BSF and set the REGB bit, otherwise the instruction is skipped. This sequence requires four instructions. A more efficient technique is to assume the bit in REGA is clear, and clear the REGB bit, and test if the REGA bit is clear. If so, the assumption was correct and the BSF instruction is skipped, otherwise the REGB bit is set. The sequence in the second example uses three instructions because one bit test was not needed. One important point is that the second example will create a two-cycle glitch if REGB is a port outputting a high. This is caused by the BCF and BTFSC instructions that will be executed regardless of the bit value in REGA. © 2008 Microchip Technology Inc. Page 1-13 8-pin Flash PIC® Microcontroller Tips ‘n Tricks TIP #18 Swap File Register with W TIP #19 Bit Shifting Using Carry Bit Example 18-1 Rotate a byte through carry without using RAM variable for loop count: SWAPWF MACRO XORWF XORWF XORWF ENDM REG REG,F REG,W REG,F The following macro swaps the contents of W and REG without using a second register. Needs: 0 TEMP registers 3 Instructions 3 TCY Example 19-1 LIST P=PIC12f629 INCLUDE P12f629.INC equ 0x20 buffer An efficient way of swapping the contents of a register with the working register is to use three XORWF instructions. It requires no temporary registers and three instructions. Here’s an example: W REG Instruction 10101100 01011100 XORWF REG,F 10101100 11110000 XORWF REG,W 01011100 11110000 XORWF REG,F 01011100 10101100 Result Page 1-14 • Easily adapted to serial interface transmit routines. • Carry bit is cleared (except last cycle) and the cycle repeats until the zero bit sets indicating the end. bsf rlf bcf btfsc bsf bcf rlf movf btfss goto STATUS,C buffer,f GPIO,Dout STATUS,C GPIO,Dout STATUS,C buffer,f buffer,f STATUS,Z Send_Loop ;Set 'end of loop' flag ;Place first bit into C ;precondition output ;Check data 0 or 1 ? ;Clear data in C ;Place next bit into C ;Force Z bit ;Exit? © 2008 Microchip Technology Inc. Tips ‘n Tricks NOTES: © 2008 Microchip Technology Inc. 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Chandler Blvd. • Chandler, AZ 85224-6199 Information subject to change. The Microchip name and logo, the Microchip logo, dsPIC, MPLAB, PIC, PICmicro and PICSTART are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. FilterLab, MXDEV and MXLAB are registered trademarks of Microchip Technology Incorporated in the U.S.A. ICSP, MPASM, MPLIB, MPLINK, PICkit, PICDEM, PICDEM.net and PICtail are trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. SQTP is a service mark of Microchip Technology Incorporated in the U.S.A. All other trademarks mentioned herein are property of their respective companies. © 2008, Microchip Technology Incorporated. All Rights Reserved. Printed in the U.S.A. 2/08