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Getting the O in I/O to work on a typical microcontroller Activating a FLASH memory “output line” Part 1 Main part of Laboratory 1 Also needed for “voice.

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Presentation on theme: "Getting the O in I/O to work on a typical microcontroller Activating a FLASH memory “output line” Part 1 Main part of Laboratory 1 Also needed for “voice."— Presentation transcript:

1 Getting the O in I/O to work on a typical microcontroller Activating a FLASH memory “output line” Part 1 Main part of Laboratory 1 Also needed for “voice activated car control project”

2 Agenda Processors need to send out control signals (high / low 1 / 0 true / false) –General purpose input / output lines (GPIO lines) on processor chip (16) –FLASH memory chip has additional I/O ports connected to Ez-Lite KIT LED’s What do we need to have happen to make the FLASH memory work on a microcontroller as we want. (In this example turning the board LED’s on and off) What new Blackfin assembly language instructions do we need to learn in order to operate the LEDs? Blackfin BF533 I/O2

3 Programmable Flags Most micro-controllers have general purpose input or output lines capable of generating “true” or “false” values Blackfin 533 has 16 GPIO lines Blackfin BF533 I/O3

4 Where are the GPIO pins found? Blackfin BF533 I/O4

5 GPIO lines are very useful They are used to sent control signals to many of the peripherals that are found on the Blackfin Evaluation Board. –Video Control –Audio Control –Input -- Buttons – GPIO PF8, 9, 10, 11 –Output – GPIO PF0, 1, 6, 7 –SPI interface control -- PF5 –Pins are functionally multiplexed – meaning pins can perform different functions at different times. Blackfin BF533 I/O5

6 Additional I/O pins available Blackfin BF533 I/O6

7 Need to control LED on board Controlled using special “additional” parallel port interface attached to “flash” memory chip Blackfin BF533 I/O7 PROJECT USE LEDs used to indicate direction radio-controlled car will move LEFT RIGHT FORWARD BACK CONTROL ON

8 FLASH MEMORY UNIT Major task -- Contains the code need to “boot” (start) the processor Blackfin BF533 I/O8 2 PSD4256G6V From STMicroElectronics The FLASH part we need during Lab. 1 Additional I/O pins

9 LEDs connected to FLASH port Blackfin BF533 I/O9 BACK FORWARD RIGHT LEFT ??? CONTROL ON These pins are connected to other things on the board DON’T CHANGE BEHAVIOUR

10 Steps to activating LEDs Get the FLASH memory to work correctly –Write the code for InitFlashASM( ) Get the Port to work correctly as output for pins PB5  PB0, leaving other pins unchanged –Write the code for InitFlashPortASM( ) Write the value we want to LEDs –WriteFlashLEDASM( int value) Read back the value the LEDs show –int ReadFlashLEDASM( ) Blackfin BF533 I/O10

11 FLASH MEMORY UNIT Controlled through “EBIU” External Bus Interface Unit EBIU are common on most processors (although often by different name) Blackfin BF533 I/O11 FLASH SDRAM CONTROLLER

12 Key information about EBIU Three busses come into the EBIU from the Blackfin processor core Forwards data to SDRAM and FLASH –How does EBIU “know” whether data is to go to FLASH or SDRAM units????? Blackfin BF533 I/O12

13 SDRAM and FLASH In later laboratories –we will build a stand-alone microcontroller system, which means we will need to understand how to program the flash memory so that the processor “knows” what to do when powered-up. Common practice on processors for boot process reads start up code from FLASH –we will need to process “large arrays” – too large to fit into the “internal fast” Blackfin “L1” memory so they must be placed in SDRAM. Common practice on processors In this laboratory, we need to program the “extra” FLASH chip I/O pins which are connected to the LED’s – control the lights now, control car later. Blackfin BF533 I/O13

14 What we know When the processor powers up – it must read its “boot” program from the FLASH The processor does not know what sort of FLASH it will be connected to When processor powers up, it will “assume” that it is connected to “slowest FLASH” in existence. (common practice) The first part of the program the processor reads in (boot code) can change the processor to read FLASH more efficiently (faster) Blackfin BF533 I/O14

15 Controlling FLASH operation Blackfin BF533 I/O15 What we need to worry about It is common for most microcontroller peripherals to have a “GLOBAL” control register and one or more “specific” control registers

16 InitFlashASM( ) Get the FLASH memory to work correctly May be “many” processes (threads) running on the Blackfin evaluation board (e.g. Audio). All these processes (threads) may want to use the flash memory for other purposes – meaning InitFlashASM( ) may have already been called by another thread before you use it InitFlashASM( ) { /* Concept only */ If FLASH memory already configured – return without changing the initialization Else { configure Memory Bank control register THEN configure Global control (turns on the FLASH) } Blackfin BF533 I/O16

17 Set the Bank control register Reset value will probably work “as is” but not efficient – “slow reads” by default (common practice for hardware) Blackfin BF533 I/O17 Default Slow (15 cycle) read and write operations

18 Settings control access speed Blackfin BF533 I/O18 DEFAULT Processor sends out address and waits 15 cycles before “do a read operation” to memory. The processor waits another 15 cycles before the actual read occurs.

19 Set General Control Register Reset value leaves “CLKOUT” disabled – is that important? Blackfin BF533 I/O19 What parts of the operation of this register must we “know” Unanswered at this time. We don’t know what needs to be known

20 InitFlashPortASM( ) Get the Port to work correctly as output for pins PB5  PB0, leaving other pin behaviour (6 and 7) unchanged. Documentation says the “Flash Direction” register allows you to choose whether the pin works as an “in” pin or works as an “out” pin (common practice) Blackfin BF533 I/O20

21 InitFlashPortASM( ) Get the Port to work correctly as output for pins PB5  PB0, leaving other pins unchanged. (Set as “Output” to control the lights) Blackfin BF533 I/O21 Used during Write and Read operations Leftmost LED 5 LED 4 LED 3 LED 2 LED1 LED0

22 Key issues -- InitFlashPortASM() Set direction to 1 (output) on lower 6 pins leaving other direction values unchanged NEED TO REVIEW ENCM369 – OR assembly code instruction needed – 8 bit values (byte) –Read EBIU “direction” register into processor core data register (makes a copy) (HOW?) –Set another processor data register to 0x3F ( ). Need to know basic binary and hexadecimal patterns for common numbers – decimal confusing when used to show “on” and “off” values – no calculators allowed in exams and quizzes –OR the two data registers (HOW?) –Write “modified copy” back into “direction register” (HOW?) PROBLEM to overcome – how do we do “byte” read and writes to Blackfin memory using “C++”? Blackfin BF533 I/O22

23 WriteFlashLEDASM( ) Write ‘1’ (on) or ‘0’ (off) to the Port to activate LEDs connected to pins PB5  PB0, leaving other pins on that port unchanged in value. (common practice) Blackfin BF533 I/O23 Leftmost LED 5 LED 4 LED 3 LED 2 LED1 LED0

24 Key issues WriteFlashLEDASM( in_value) Write ‘1’ (on) or ‘0’ (off) to the Port to activate LEDs connected to pins PB5  PB0, leaving other pins unchanged. –Read “LED data register” into processor data register (makes a copy in R0) – 8-bit byte –Keep “top” 2 bits (AND operation) of copy (8 bit) –Keep “bottom” 6 bits of “in-par” 32-bit in_value that is passed into the subroutine –OR the two processor data registers (32 and 8) –Write “modified copy” back into “LED data register” – 8-bit byte PROBLEM mixed “byte (8)” and “long word (32)” operations Blackfin BF533 I/O24

25 Things we need to learn How do we put a 32-bit value (long int) into a register (data Rn or pointer Pn)? How do we put an 8 or 32-bit value into memory? How do we handle byte operations (8- bit)? How do we do AND and OR operations on Blackfin? How similar is Blackfin to MIPS when handling these issues (ENCM369)? Blackfin BF533 I/O25

26 Agenda tackled Processors need to send out control signals –General purpose input / output GPIO on processor Not enough GPIO lines –FLASH memory chip has additional I/O ports connected to Ez-Lite KIT LED’s What do we need to have happen to make the FLASH memory work as we want? What new Blackfin assembly language instructions do we need to learn? Blackfin BF533 I/O26


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