University of Texas at El Paso Electrical and Computer Engineering Department

Transcription

1 University of Texas at El Paso Electrical and Computer Engineering Department EE 3176 Laboratory for Microprocessors I Fall 2016 LAB 07 Flash Controller Goals: Bonus: Pre Lab Questions: Familiarize yourself with the provided Flash Controller library and learn how to read and write Flash Memory. Store three 4-digit numbers in the MSP430 s flash memory. Use the # button to store an entry and the * button to delete an entry. Indicate a blank entry as XXXX. Scroll through the entries using the on-board button on the MSP430 launchpad or an external switch. Have the micro display info on the LCD Display. This lab can be done without interrupts but see if you can find a way to use one anyway. +10 Which memory segment did you use? Why? Why use flash memory to store data? What variable data type did you use to store the digits? How did you decide what button was pushed?

2 Lab Guide 12 Button Keypad The 12 Button Keypad has 7 pins: 4 pins are connected to each row, while 3 pins are connected to each column. See the diagram below: Rows 1 Columns Pins: When you push a button, a connection is made and a voltage can be detected to determine what button was pushed. The provided method first sets all column pins as inputs and row pins as outputs. A column is activated by enabling the input resistor associated with that pin and setting each row pin high, one by one. The process is repeated for each column pin. Any input is then recorded and encoded as an 8bit keycode described below: KEYCODE Bits Pins X Row/Column R1 R2 R3 R4 C1 C2 C3 X Example: Keycode = means the 1 key was pressed; Keycode = means the 1 and 0 keys were pressed.

3 Flash Memory and Controller Your program and data is stored in Flash Memory. There are two sections in which you can right data; the Code/Data Section and the Information Section. Each section is divided up into segments. The Code /Data Section has 32 segments, 0-31, 512 bytes each, while the Information Section has 4 segments, A D, 64 bytes each. However, Segment A is locked because it contains calibration data for the micro s clock and other info that you will not want deleted. Data can be written a bit, byte or word at a time, randomly, but in order to erase data, an entire segment must be erased before new data can be written. MEMORY MAP Section Segment Address Size Interrupt Vector 0xFFC xFE00 1 0xFC00 2 0xFA00 3 0xF xF xF xF xF xEE00 9 0xEC xEA xE xE xE xE xE000 Code/Data xDE xDC xDA xD xD xD xD xD xCE xCC xCA xC xC xC xC xC000 A 0x10C0 B 0x1080 Information 64 C 0x1040 D 0x1000 RAM 0x0200 0x03FF bit 0x0100 0x01FF 256 Peripherals 8-bit 0x010 0x0FF bit SFR 0x00 0x0F 16

4 Notes: Trying to write incorrect data to an address will corrupt it, resulting in all zeros (0x0000). The Interrupt Vectors and Code/Data sections overlap. When writing word data into an address, it is stored LSB first. Example: data = 0x0201 into address = 0xF000: DATA STORE Address 0xF000 0xF001 Data 0x01 0x02 Byte LSB MSB Only Segments of the same size can be moved or copied to: Example: Code / Data Segments (Segment 0-31) = 512 and Information Segments (Segments A - D) = 64 Note that Segment A is locked. It can be unlocked but it contains calibration data that you will miss if you delete it. It CANNOT be recovered.

5 Lab Hints There is no sample code to start with; instead you must know enough by now to be able to write the program from scratch. However, the general program flow will be described below: Include necessary headers Declare necessary global variables Initialize and configure necessary modules (Ports, Interrupts) You may poll or use interrupts to capture keypresses You can use interrupts to execute short code (perhaps to loop through the stored digits) and have your main loop handle the main functions, such as write and erase, and to display your data on the LCD display. Data should survive power failure. Check the comments in source files/libraries provided. Make sure you understand what is happening in the sample programs provided.

6 Post Lab Lab Notebook Questions: Answer the following questions in your lab notebook: Why not store data in RAM? Why is it difficult to write data bit per bit? Why does a whole memory segment have to be erased before writing new data? How does flash memory differ from other types of memory such as RAM?

7 Frequently Asked Questions Why is the method used for writing blocks of data from the provided library not considered a true block write? First, a true block write is possible with the MSP430G2553, however, block writes must be initiated from RAM. This means the provided method can be used for writing blocks of data but it must be copied to RAM at runtime (and also modified slightly). In order to write data, a programming voltage is used by the flash controller to program a word of data into the specified address. The voltage is raised when writing and lowered when the write is finished. A true block write keeps the voltage high throughout the programing of the entire block, whereas the provided method in the library is raised and lowered in between the writing of each word in the block. So what s the advantage of that? There is a current differential that comes with raising and lowering the voltage in this fashion, which consumes more power. Keeping the voltage raised throughout writing a bunch of data saves power. See the Flash Controller section in the User Guide for more details. Does the Flash Controller have an ISR? Not one of its own. The Flash Controller sources the NMI (Non-Maskable Interrupts) vector, even though the Flash Controller interrupt is totally maskable. However, it is only triggered when there is a flash memory access violation (such as not using the flash password for access) and a PUC (Power Up Clear) usually occurs. As such, you can only use the interrupt to determine if an access violation has occurred but usually you can t do anything about it anyway.