160 lines
5.3 KiB
Markdown
Executable File
160 lines
5.3 KiB
Markdown
Executable File
*These notes are intended to highlight bits of information from the
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Xilinx KCPSM3 manual distributed with the microprocessor*
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**Xilinx Picoblaze**
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KCPSM3 - An 8 Bit Microcontroller for Xilinx Spartan 3 & Virtex 2/4
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devices
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**What is kcpsm3**
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Very Simple microcontroller. Can be used for data processing or as a
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complex state machine.
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**KCPSM** - (**K**)constant **C**oded **P**rogrammable **S**tate
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**M**achine
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Its very small - 96 Spartan3 slices + 1 block ram
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Our boards - 4656 slices -\> that is 2% of the slice resources!
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Entirely embedded in the fpga fabric - integrates with all the logic
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you've already been writing!
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**kcpsm is small**
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Konstant explained - notice how the mips = 1/2 clock speed?
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CPI of the processor is 2. And fixed at 2. that makes it very easy to
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determine the runtime of a program in an embedded system.
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**kcpsm3 architecture**
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architecture is closed (it is a xilinx macro, not a readily readable
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verilog design) but the architecture is not secret though
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simple input port/output based IO, up to 256 addressable 8bit
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ports/devices 16 general purpose registers 64 byte memory/scratch pad
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alu with carry/zero flags single interrupt line/acknowledge program
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counter control/instruction decoder program memory
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**device features**
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program memory - 1 18kb block ram! this stores 1024 18 bit instructions.
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16 general purpose registers. No dedicated zero register or accumulator
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alu - does add/sub/add&sub with carry alu - load/and/or/xor bitwise
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alu - shift/rotates flags and flow control - help determine program flow
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with carry/zero flags + conditional jump/call instructions interrupts -
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jumps to a single address (initiates CALL 3FF) - an ISR
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**using the kcpsm3** used as a verilog module in the design flow. simply
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copy the kcpsm3.v file into your project and instantiate it kcpsm3
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assembler generates a verilog memory file - use that in your design as
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well. connect the two modules together. alternatively - use the
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embedded_kcpsm3.v file
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**instruction set**
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1. program control group
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1. unconditional jump
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2. conditional jumps (branches!)
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3. call/return with stack depth of 31
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2. interrupt group
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1. enable/disable interrupt
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2. return from isr & either enable/disable the interrupt
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3. storage group
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1. store/fetch data from the scratch pad
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4. i/o group
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5. arithmetic group
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1. add/sub/compare
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1. work with 2 operands or 1 operand and a constant
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6. logical group
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1. load/and/or/xor/test
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1. work with 2 operands or 1 operand and a constant
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7. shift/rotate group
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1. both left/right shifts available
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pointers available
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**port access**
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input and output ports available.
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very simple with the two cycle operation
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1. 1st cycle - instruction decode
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2. 2nd cycle - instruction execute
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Read strobe - not needed, port_id used w/ a mux to determine what gets
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put on input port. data captured by kcpsm3 on next clock edge.
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write strobe - use as a clock enable signal for external circuitry to
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capture data from out port.
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\<8 output ports, use 1hot addressing
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\>8 output ports, use address decoder to enable the correct port
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input ports -\> leads itself to a multiplexed architecture
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**reset**
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synchronous to kcpsm3 clock. blanks the processor and restarts it at
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address 0x000.
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**picoblaze assembler**
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xilinx assembler is a dos program, which accepts .psm (picoblaze
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assembler) source files and outputs vhdl/verilog files for your use
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multipass, lots of quick information. don't be afraid to dump the file.
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possible to run under wine/dosbox, lots of alternatives available.
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**program syntax**
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1. blank lines are ignored
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2. comments begin with ;
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3. registers - form sX, where X={0,1,2,..9,A,...,E,F}
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4. constants
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5. Data value - 00 -\>FF
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6. Port value - 00 -\>FF
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7. Address - 000 -\>3FF
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8. Line labels: Useful for call and jump instructions!
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constant -\> define a label used within the program for holding a
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constant value. like a C macro
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namereg -\> define a label used within the program for identifying a
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register. allows for much more readable code.
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**Interrupts**
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slides are really detailed about this and good - read them
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**call/return stack**
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31 level call/return stack. program counter preserved upon the calll
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instruction or interrupt. registers are not preserved - be careful not
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to clobber your registers.
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**simulation** picoblaze assembly simulators exist - \> prove your code
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by hand (slow) nothing stopping you from simulating the HDL design - but
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can be very slow. quicker to fix hardware design -\> then code and
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download to picoblaze via jtag and run the software.
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**other picoblaze ide/assemblers/simulators/implementations that are not
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from xilinx**
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1. **pacoblaze** [Pacoblaze](http://www.bleyer.org/pacoblaze/)
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opensource, picoblaze compliant verilog implementation. complete
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with java assembler.
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2. **openPicIDE** [openPicIDE](http://www.openpicide.org/) opensource
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picoblaze ide/assembler/simulator. very robust! works on linux, mac,
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windows.
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3. **mediatronix picoblaze ide**
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[mediatronix](http://www.mediatronix.com/tools/index.htm) amazing
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windows picoblaze ide
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4. **kpicosim** [kpicosim](http://www.xs4all.nl/~marksix/) picoblaze
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simulator and assembler. linux
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[Category:FPGAWorkshop](Category:FPGAWorkshop "wikilink") |