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''These notes are intended to highlight bits of information from the Xilinx KCPSM3 manual distributed with the microprocessor'' | |||
'''Xilinx Picoblaze''' | '''Xilinx Picoblaze''' | ||
Latest revision as of 17:04, 3 April 2012
These notes are intended to highlight bits of information from the Xilinx KCPSM3 manual distributed with the microprocessor
Xilinx Picoblaze
KCPSM3 - An 8 Bit Microcontroller for Xilinx Spartan 3 & Virtex 2/4 devices
What is kcpsm3
Very Simple microcontroller. Can be used for data processing or as a complex state machine.
KCPSM - (K)constant Coded Programmable State Machine
Its very small - 96 Spartan3 slices + 1 block ram
Our boards - 4656 slices -> that is 2% of the slice resources!
Entirely embedded in the fpga fabric - integrates with all the logic you've already been writing!
kcpsm is small
Konstant explained - notice how the mips = 1/2 clock speed?
CPI of the processor is 2. And fixed at 2. that makes it very easy to determine the runtime of a program in an embedded system.
kcpsm3 architecture
architecture is closed (it is a xilinx macro, not a readily readable verilog design) but the architecture is not secret though
simple input port/output based IO, up to 256 addressable 8bit ports/devices 16 general purpose registers 64 byte memory/scratch pad alu with carry/zero flags single interrupt line/acknowledge program counter control/instruction decoder program memory
device features
program memory - 1 18kb block ram! this stores 1024 18 bit instructions. 16 general purpose registers. No dedicated zero register or accumulator alu - does add/sub/add&sub with carry alu - load/and/or/xor bitwise alu - shift/rotates flags and flow control - help determine program flow with carry/zero flags + conditional jump/call instructions interrupts - jumps to a single address (initiates CALL 3FF) - an ISR
using the kcpsm3 used as a verilog module in the design flow. simply copy the kcpsm3.v file into your project and instantiate it kcpsm3 assembler generates a verilog memory file - use that in your design as well. connect the two modules together. alternatively - use the embedded_kcpsm3.v file
instruction set
- program control group
- unconditional jump
- conditional jumps (branches!)
- call/return with stack depth of 31
- interrupt group
- enable/disable interrupt
- return from isr & either enable/disable the interrupt
- storage group
- store/fetch data from the scratch pad
- i/o group
- arithmetic group
- add/sub/compare
- work with 2 operands or 1 operand and a constant
- add/sub/compare
- logical group
- load/and/or/xor/test
- work with 2 operands or 1 operand and a constant
- load/and/or/xor/test
- shift/rotate group
- both left/right shifts available
pointers available
port access
input and output ports available.
very simple with the two cycle operation
- 1st cycle - instruction decode
- 2nd cycle - instruction execute
Read strobe - not needed, port_id used w/ a mux to determine what gets put on input port. data captured by kcpsm3 on next clock edge.
write strobe - use as a clock enable signal for external circuitry to capture data from out port.
<8 output ports, use 1hot addressing
>8 output ports, use address decoder to enable the correct port
input ports -> leads itself to a multiplexed architecture
reset
synchronous to kcpsm3 clock. blanks the processor and restarts it at address 0x000.
picoblaze assembler
xilinx assembler is a dos program, which accepts .psm (picoblaze assembler) source files and outputs vhdl/verilog files for your use multipass, lots of quick information. don't be afraid to dump the file.
possible to run under wine/dosbox, lots of alternatives available.
program syntax
- blank lines are ignored
- comments begin with ;
- registers - form sX, where X={0,1,2,..9,A,...,E,F}
- constants
- Data value - 00 ->FF
- Port value - 00 ->FF
- Address - 000 ->3FF
- Line labels: Useful for call and jump instructions!
constant -> define a label used within the program for holding a constant value. like a C macro
namereg -> define a label used within the program for identifying a register. allows for much more readable code.
Interrupts
slides are really detailed about this and good - read them
call/return stack
31 level call/return stack. program counter preserved upon the calll instruction or interrupt. registers are not preserved - be careful not to clobber your registers.
simulation picoblaze assembly simulators exist - > prove your code by hand (slow) nothing stopping you from simulating the HDL design - but can be very slow. quicker to fix hardware design -> then code and download to picoblaze via jtag and run the software.
other picoblaze ide/assemblers/simulators/implementations that are not from xilinx
- pacoblaze Pacoblaze opensource, picoblaze compliant verilog implementation. complete with java assembler.
- openPicIDE openPicIDE opensource picoblaze ide/assembler/simulator. very robust! works on linux, mac, windows.
- mediatronix picoblaze ide mediatronix amazing windows picoblaze ide
- kpicosim kpicosim picoblaze simulator and assembler. linux