Lab 3: Implementing Functions with the Simon Board 1 Intro to the
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1. When the pin is driven low it is driven strongly and able to sink a large current There are three pull up transistors in the quasi bidirectional output that serve different purposes e One of these pull ups called the very weak pull up is turned on whenever the port latch for the pin contains a logic 1 This very weak pull up sources a very small current that will pull the pin high if it is left floating e A second pull up called the weak pull up is turned on when the port latch for the pin contains a logic 1 and the pin itself is also at a logic 1 level This pull up provides the primary source current for a quasi bidirectional pin that is outputting a 1 If this pin is pulled low by an external device the weak pull up turns off and only the very weak pull up remains on In order to pull the pin low under these conditions the external device has to sink enough current to overpower the weak pull up and pull the port pin below its input threshold voltage e The third pull up is referred to as the strong pull up This pull up is used to speed up low to high transitions on a quasi bidirectional port pin when the port latch changes from a logic 0 to a logic 1 When this occurs the strong pull up turns on for two CPU clocks quickly pulling the port pin high Will I ever need more current on the Simon Board For LED s and the Speaker P1 7 a very small current is needed microamps range therefore Bi directional2. there are two primary modes that are frequently used e 16 bit mode which uses two registers Hx and TLx to load with the count value e 8 bit auto reload mode THx holds the load reload value and TLx is the timer itself Once the timer values are loaded and the timer is turned on then the timer begins to count upward until it overflows in unsigned binary to OH When the overflow is detected it throws the flag TFx This TFx can be periodically checked in your program to determine when it has overflowed This can help us create very tight delays and thus generate actions that operate at given intervals frequencies e TIMERS ON THE SIMON BOARD ARE CONFIGURED EXACTLY THE SAME AS THE REFER ENCE 8051 Generating a Frequency One of the first concepts you will learn is how to determine how long an instruction or a timer s tick takes in time space Two variables 1 Clock oscillator 2 Clock cycles per Machine Cycle A Machine Cycle can be thought of as going through Fetch Decode Execute e THE SIMON BOARD s LPC932A1 USES 2 CLOCK CYCLES MACHINE CYCLE Square wave assumption For the most pure frequency it is assumed that you will be generating an action with a 50 duty cycle This is particular important when considering the signal processing and electromagnetic effects in transmission line circuits found on your typical PCB Suppose we have an action we d like to do at a 5K Hz rate Let us take the two variables ment
3. 32A1 every single Port P0 P3 are initialized upon reset as an input only as shown in Figure 4 input PORT glitch rejection FIG 4 Input only default for PO P3 However many times you want to work with the LED for example This is going to require some form of output mode for these pins P2 7 2 4 There are two possiblities to achieve this Bi directional mode and Open drain mode e Let s look at Open Drain mode first in Figure 5 If the Port bit say P2 7 is set to a 0 then the NMOS transistor provides a path to GND The LED s on the board are biased in such a way where this NMOS acts as a switch for them However the current is limited to the impedances in the KVL path port latch glitch rejection FIG 5 Open Drain mode e The other choice is Bi directional This is a popular choice and probably what you will want to work with primarily in your projects It has the ability to be both an input and an output pin This is shown in Figure 6 VDD glitch rejection FIG 6 Bi directional mode So what s the catch to this mode In a nutshell you give up not being able to drive as much output current Here is a concise description of the 3 PMOS transistors from the datasheet e Quasi bidirectional outputs can be used both as an input and output without the need to reconfigure the port This is possible because when the port outputs a logic high it is weakly driven allowing an external device to pull the pin low
4. Discuss how you would implement a function that sends different tones through the speaker on the board based upon a given button press Reference P89LPC932A1 User Manual Koninklijke Philips Electronics N V 2004 All rights reserved
5. Lab 3 Implementing Functions with the Simon Board CpE 214 Digital Engineering Lab II Last revised January 25 2013 CAC You will extend your knowledge of the original 8051 reference design to that of newer 80C51 derivatives The Simon Board developed here at Rolla which features a more modern 8051 based architecture will be introduced The student will learn in assembly language ASM how to configure the port modes enable disable Special Function Registers learn to debounce signals and perform a simple timing program Upon completing the lab a broader understanding of embedded hardware implementations and how to write software for them is achieved 0 1 Outline and Concepts 1 Intro to the Simon Board clock sources 2 Port mode configurations How the timers work generating frequencies oe WwW Writing the ASM program 5 Flashing and testing 1 Intro to the Simon Board clock sources The Simon Board pictured in Figure 1 will be used in your course projects and sometimes make their way into other lab course senior projects here in the department In the 213 lecture you spend most of your time learning the generalized features functions of the original 8051 reference design and for good reason However one of the most common mistakes that students typically make in their projects is to attempt to use certain special functions that are hardware specific to the individual chip with code configurations straight o
6. and use the settings as shown in Figure 9 below e Be sure to Move the Jumper on the Simon Board to ISP instead of Run first before hitting start Flash Magic NON PRODUCTION USE ONLY File ISP Options Tools Help OHAJ SYR SaL Step 1 Communications Step 2 Erase COM Port COM 1 Erase block 0 0x0000 0x03FF Erase block 1 0x0400 0x07FF Baud Rate 7200 v Erase block 2 0x0800 0x0BFF Erase block 3 0x0C00 0x0FFF Device B9LPC932A1 Z Erase block 4 0x1 000 041 3FF Interface None ISP Erase block 5 0x1 400 01 7FF Erase all Flash Oscillator Freq MHz J Erase blocks used by Hex File Step 3 Hex File Hex File S CpE 214 labs lab lab 7 hex Browse Modified Tuesday May 10 2011 5 22 55 PM more info Step 4 Options Step 5 Start Verity after programming Block 0 Sec Bit 0 al Start Fill unused Flash _ Block 0 Sec Bit 1 a Gen block checksums Block 0SecBit2 gt Execute On Line training classes for microcontrollers and embedded networking and Internetworking www esacademy com fag classes gt De eee FIG 9 Flash Magic settings 6 Questions attach at end of your report 1 Discuss what you should consider before choosing a port mode configuration push pull bi directional open drain input only 2 List a few things you should always check before writing software routines for an 8051 or any platform embedded device 3
7. ioned earlier and do a unit multiplication division to determine what is needed Fosc clock cycles 1 machine cycle Y machine cycles _ _ or Z sec machine cycle 1 sec X clock cycles sec e A clock tick takes a single machine cycle Therefore for a 5KHz action you would need to perform it every 1 5000 seconds IF YOU ARE GENERATING A WAVE YOU MUST COMPLEMENT THE SIGNAL EVERY HALF PERIOD or 1 10000 seconds Do I need 16 bit or 8 bit auto reload mode Good question A typical rule is that low frequencies generally need the full 16 bits since they are slower to delay long enough However in many cases 8 bit auto reload is sufficient Remember from the previous section PCLK is the oscillator for the Timers which by default is 7 3728MHz 2 You need to work the math out to be certain 4 Writing the ASM program For your program you need to use the Keil Microvision software It is an assembler and compiler for the generalized 8051 platform often called 80C51 Appendix C can be used as a reference for Keil and below outlines a general walkthrough for getting a new project going oe A WwW bd ie 8 Open Keil gt Project gt Create New Project On Device ID choose Generic gt 8051 On the left hand side Right click on Targetl gt Target Options gt Output tab gt Check Create Hex File on A51 Tab uncheck Define 8051 SFR s Don t skip this step or you will get compiler redefinition err
8. mode is just fine The Serial Port UART is the only interface that typically needs more current and that is easily rectified with an alternate mode called Push Pull e Push Pull mode Push pull mode provides a continuous strong pull up when the port pin has output a latched 1 This is shown in Figure 7 The strong meaning that the PMOS is very wide thus having a smaller resistance which allows via Voltage Divider principle to drop more Voltage and drive more current through the load Since the UART serial port typically requires an external IC to convert 0 and VDD signals of our microcontroller into the RS 232 voltage signaling which are higher voltages it is expected that more current is likely needed Vpop port latch input data glitch rejection FIG 7 Push pull mode for more current How do I set the Modes This is pretty simple There are two registers you need to work with to set a particular port to your given mode of choice PxM1 and PxM2 the x stands for the Port number Figure 8 shows the Table from the datasheet for how to set the modes to what you want REMEMBER ALL PORTS START AS INPUT ONLY PxM1 y PxM2 y Port output mode 0 0 Quasi bidirectional 0 1 Push pull 1 0 Input only high impedance 1 1 Open drain FIG 8 Port Mode configuration bits 3 How the timers work generating frequencies We won t cover intimately how the timers work You will cover this in detail in the lecture In short
9. note of CCLK and PCLK These are the two most important Clock lines Both come from OSCCLK which can use the DIVM register to divide down slow down the clock frequency e CCLK goes to your main CPU functions i e exectution of your ASM instructions in your routines e PCLK is just CCLK 2 and is the clock provided to the special function Timers and the Serial Port UART etc OSCCLK is chosen by a 4 1 MUX with the select lines determined by a few different registers Let s look at them briefly in Figure 3 FOSC2 0 RCCLK RTCS1 0 RTC clock source CPU clock source 011 0 00 High frequency crystal intemal RC oscillator 01 Medium frequency crystal OIVM 10 Low frequency crystal 11 Internal RC oscillator IDIVM FIG 3 OSCCLK select bit options FOSC2 0 is located in the flash bit register UCFG1 RCCLK is located in TRIM register and RT CS1 0 is located in the RTCCON register All can be found in the datsheet if you need to look them up The Default Configuration CCLK RTC INTERNAL RC OSCILLATOR DIVM We have preconfigured the Simon Board in the flash bootloader with the internal RC oscillator DIVM as the CCLK line If you ever need to change it unlikely you can with the information above 2 Port mode configurations One area that is typically undercovered in the lecture is how to deal practically with port mode configurations This requires some basic electrical knowledge none of which is difficult For the Simon Board s LPC9
10. ors Close out and Then go to File gt New Create a new file and save it in your project s folder with a filename ad1 extension On the left hand side right click on Source Group under Target1 and choose Add Files Add your file you just saved This is needed so it will be included in the compiler Finally at the top of your file you need to include just like in C a header include lt reg932 inc gt This file can be found on Blackboard and needs to be copied into your project s folder Don t add it to your source group list in Keil itself PROGRAM REQUIREMENTS 1 Setup the Push buttons and LED s to light up when their respective button below each is pushed The Simon Board schematic on Blackboard can be helpful for this 2 Develop a way to debounce the push buttons where the signal is only recognized a single time You may need to experiment with this to ensure reliability 3 Each time a button is pressed generate a square wave of 1OKHz on the speaker P1 7 You can use any timer mode Your textbook can also be useful for the Timer portion for examples NOTE THAT THE BUTTONS AND LED S ARE ACTIVE LOW 5 Flashing and testing For flashing your hex file that you have generated from your compiled code you will need to use the Flash Magic software Connect the RS 232 cable to the serial ports on the Simon Board and the PC and then you are ready to flash You will need to browse select your hex file
11. ut of the textbook Some things work exactly the same and some things don t In this lab you will learn how read a chip s datasheet to determine this information a critical skill you need to develop as an ECE FIG 1 Simon Board What features does it have What can it do e 4 LED s 4 push button inputs e 2 different oscillator clocks 7 3728MHz RC internal 11 0592MHz PLL external e Philips LPC932A1 which features onboard Flash ROM 2 GP timers 12C interface and 1 ded serial port timer e Serial port for bidirectional communication and flashing of ROM e External jumpers for PO P1 and P2 buses as well as XTAL 3 3V and GND rails e The Most Important Thing you need to be aware of Clock oscillator options In the 8051 context you re used to there is a single oscillator and it drives all functions of the device In modern designs like the LPC932A1 this is not the case There is a buffet of options at your disposal to choose from Typically for most people you never need to change from the default configurations at reset but IT IS IMPORTANT TO KNOW WHAT ARE THE DEFAULTS The oscillator schematic for the Simon Board is shown below in Figure 2 XTAL 4 HIGH FREQUENCY Oom MEDIUM FREQUENCY RTC XTAL2 LOW FREQUENCY B cPu RC RCCLK OSCILLATOR 2 7 3728 MHz 1 PCLK OSCILLATOR a aoe 32 x PLL 400 kHz 3p x CCU TIMER 0 AND FIG 2 Oscillator diagram taken from p 21 of datasheet Take
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