1. PicoBlaze CPLD Microcontroller

2. Agenda What is PicoBlaze PicoBlaze operation PicoBlaze software flow
Customize PicoBlaze
Memory integration
Why PicoBlaze

3. What is PicoBlaze?
A fully customizable 8-bit soft microcontroller macros that provides
49 16-bit instructions
8 general-purpose 8-bit registers
256 directly and indirectly addressable ports
Reset and a maskable interrupt
PicoBlaze is a fully embedded 8-bit microcontroller originally targeted to Virtex and Spartan-II devices.
The CR-II version has the same instruction set as FPGA version
FGPA has 16 general-purpose 8-bit registers, CR-II uses 8 only
256 port addresses can be specified directly by constant or indirectly by the value of a register
FGPA uses block ram to store program instructions, CR-II instructions can be save in external memory or can be integrated as a big state machine.

4. PicoBlaze Block Diagram8 8
Port Address Control 8
PORT_ID
READ_STROBE
WRITE_STROBE 8 8 8
8 Registers 8-bit 8
IN_PORT
OUT_PORT 8
ALU 8
Interrupt Flag Store
ZERO & CARRY Flags
Interrupt Control
INTERRUPT
Similar to a typical microcontroller, PicoBlaze including the instruction decoding block, ALU, program counter and program counter stack, general purpose register bank and port address control.
A instruction is decoded and performed by ALU or Flow control, the result sends to a register or to a port 8
Program Counter 8
ADDRESS
Program Flow Control 16
Operational Control & Instruction Decoding
CONSTANT DATA
INSTRUCTION 8
RESET
Program Counter Stack
CLK

5. PicoBlaze Operation PicoBlaze 2 clock cycle operation IN_PORT[7:0]
OUT_PORT[7:0]
PORT_ID[7:0]
INTERRUPT
READ_STROBE
Program ROM
RESET
WRITE_STROBE
INSTRUCTION[15:0]
INSTRUCTIOIN[15:0]
ADDRESS[7:0]
ADDRESS[7:0]
CLK
CLK
2 clock cycle operation
CLK
ADDRESS(7:0) 00 01 02 03 04
INSTRUCTION(15:0)
0700
0801
F632
DC5A
RESET
User code (instructions) store in program rom
PicoBlaze fetch the instruction, execute and addressing for next instruction
All instructions under all conditions execute over two clock cycles
A constant execution rate is a great value for embedded real time design

6. PicoBlaze Instruction Set
Program Control Group
JUMP
CALL
RETURN
Logical Group
LOAD
AND OR
XOR
Arithmetic Group
ADD
ADDCY
SUB
SUBCY
Shift & Rotate Group
SR0
SR1
SRX
SRA RR
SL0
SL1
SLX
SLA RL
Input/Output Group
INPUT
OUTPUT
Interrupt Group
RETURNI ENABLE
RETURNI DISABLE
INTERRUPT ENABLE
INTERRUPT DISABLE
49 instructions in 6 groups
Q: only 27 instructions here, why?
A: reference to appendix A, program control group can be expended to 15 instructions when it combine with the flags.

7. Assembler A simple DOS executable file Written in C
Use Microsoft Visual Studio 6.0
Easy to change
The assembler is a DOS program running under DOS window
Written in ANSI C and compiled with Microsoft Visual Studio 6.0
It can be easily port to other platform
Easy to change for customization

8. Assembler Files ASM.EXE Filename.asm Filename.mcs Filename.vhd
<User input file>
ASM.EXE
<Binary code for ROM>
Filename.mcs
Filename.vhd
Filename.bin
Filename.fmt
Filename.log
<VHDL for simulation>
User writes assembly as input file
The assembler generates
Mcs file – a binary code to program the external program ROM/EPROM
Vhd file – vhdl model can be used for simulation or integration
Bin file – a binary code in hex format for debugging
Fmt file – a formatted assembly file for documentation
Log file – a report
<Binary code in hex format>
<Formatted assembly file>
<Assembler report>

9. A Simple Shifter Constant shifter_port, 04 ;declare port
Namereg s7, shifter_reg ;declare register
Loop1: Load shifter_reg, 01 ;init shifter reg
Loop2: Output shifter_reg, shifter_port
SL0 shifter_reg ;shift left with 0
Jump NZ, loop2 ;goto loop2 when s7<>0
Jump loop1 ;goto loop1
A simple example showing the syntax
Complete syntax can be found in appendix A
Constant and Namereg are directives provide a way to assign an 8-bit constant value and register to a label
Loop1 and loop2 are also address label
The first instruction is to load constant ‘1’ into shift register
2nd instruction is to output the shift register to the output port
3rd instruction shift the value left by 1 position
4th instruction checks shift register value and jump to loop2 when the value is not zero (NZ), the address pointer will go to 5 when the value equals zero
5th instruction is unconditional jump to loop1 to make an endless loop
This code is for syntax demonstration, not an optimized code

10. Shifter Program Address Hex Binary 00 0701 01 8F04 02 A706 03 D501 04 01
8F04 02
A706 03
D501 04
D000
Load s7, 01
Output s7, 04
SL0 s7
Jump NZ, 01
Jump 00
This is to show how the assembler works
The table shows the address and instruction in hex and binary format for each assembly code

11. PicoBlaze Software Flow
Compile PicoBlaze source
Use WebPACK 5.2i or later
Use FISE 5.2i or later
Assemble the program code
asm filename.asm
Download to the CPLD
iMPACT 5.2i or later
Download assembled object code to EEPROM
This is a software flow for picoblaze application development
User compiles the picoblaze vhdl by using webpack
Develop assembly code for application and run picoblaze assembler on DOS window
Download the picoblaze to cpld and assembled binary code to ROM or EEPROM

12. Making a Processor Change
Add an instruction
Modify picoblaze.vhd
Add a constant with instruction code:
constant new_instruction_id : std_logic_vector(4 downto 0) := “10101";
Add instruction decoding signal
i_new_instruction <= '1' when instruction(15 downto 11) = new_instruction_id else '0';
Define VHDL component with functionality of new instruction
Add new component to picoblaze.vhd
Tweak the assembler
Add new instruction to asm.cpp
char *new_instruction_id = “10101“;
Add case to write_program_word function of asm.cpp
Recompile asm.cpp to create asm.exe
This is to explain how to customize the picoblaze
Add an instruction to vhdl and assembler
The vhdl and c code is made very easy for customization
The code can be download from xilinx website, reference xapp387

13. Making a Processor Change
A DSP example - bit reversal (“Flip”) operation
12 to 18 instructions needed in regular microcontroller programming
A newly created FLIP function in PicoBlaze can be used to complete the operation in just one instruction cycle
This is an example to show a new instruction FLIP to do a bit reversal operation
It will take 12 to 18 instructions without create this new instruction
The new instruction can be complete in one instruction cycle

14. Macrocell Usage
This is a table to show the possible functions can be added to CR-II and their macrocell usage

15. Program Memory Integration
Binary code and processor can be integrated into a single CPLD
Eliminates external PROM
SOC solution
Reduces size
Increases performance
It is possible to integrate the external instruction memory into a single CR-II device
Dependent on applications, it can reduce the size and increase performance

16. Integration Design Flow
Assemble the design
Use PicoBlaze Assembler
asm design.asm
Generates design.vhd
Write top level VHDL
Wrap picoblaze.vhd and design.vhd (output from assembler)
Compile top level VHDL source
Use WebPACK 5.2i or later
Use FISE 5.2i or later
Download to CPLD
Use iMPACT 5.2i or later

17. 1 + 1 < 2 PicoBlaze PicoBlaze + Shifter
Macrocells
Product Terms
Registers
FB Inputs
Fmax
212/256 ( 83%)
642 /896 ( 72%)
155/256 ( 61%)
451/640 ( 70%)
30 MHz
PicoBlaze + Shifter
Macrocells
Product Terms
Registers
FB Inputs
Fmax
107/256 ( 42%)
341 /896 ( 38%)
82 /256 ( 32%)
208/640 ( 32%)
87 MHz
This is the shifter example
It uses 212 macrocells for a stand alone picoblaze core and runs 30 MHz
Once the shifter integrated into picoblaze to perform this specific task
The macrocell count reduced to 107 and speed increased to 87 MHz
- Fitter removes redundant circuits

18. PicoBlaze Demonstration
Demonstrate simple shifter
Add FLIP instruction
Exchanges bits in specified register
MSB to LSB
LSB to MSB
Modify picoblaze.vhd
Create FLIP component
Modify asm.cpp
Demonstrate FLIP instruction with new program
Here to demonstrate a newly added FLIP instruction
First to load the shifter on the part and show LED shifting
Recompile the FLIP code and download the new design to CR-II on the fly (OTF)
Show LED change from shifting into flipping instantly

19. Why Use PicoBlaze? Emulate out of production processors
Lower power consumption than older small processors
Customizable for performance
PicoBlaze runs faster than most 8-bit and16-bit uCs (PICs, 8051, 6811, 80188, 6816, etc.)
Customizable for specific applications
uCs have fixed features
uCs have fixed instructions sets
PicoBlaze can run functions quickly in parallel logic
Many advantages to use picoblaze than uCs

20. Why Use PicoBlaze? PicoBlaze is parameterized
uCs have fixed size
uCs have limited I/Os
Can be reconfigured “On the Fly (OTF)”
Cryptography/security
More advantages

21. Conclusion PicoBlaze is a soft microcontroller module
Use PicoBlaze for custom microcontroller applications
Create custom instruction sets
Program memory integration
Use PicoBlaze Assembler
Compile with current Xilinx software

22. CoolRunner-II Reference Designs
Free HDL CoolRunner-II design code download:

23. Appendix A
Instruction set descriptions
Syntax
Bit description

24. Program Syntax No blank lines – Use a semicolon for blank lines
Comments – Any item on a line following a semicolon (;)
Constant – Must be specified in the form of a 2 digit hexadecimal value(00 – FF)
Line Labels – To identify a program line for JUMP or CALL instruction should be followed by a colon (:)
CONSTANT Directive – Assigns an 8-bit constant value to a label
NAMEREG Directive – Assigns a new name to any of the 8 registers
ADDRESS Directive – Forces the following instructions commencing at a new address value

25. Program Control I C A 1 1 1 JUMP CALL RETURN Address Unconditional
JUMP aa
JUMP Z, aa
JUMP NZ, aa
JUMP C, aa
JUMP NC, aa
CALL aa
CALL Z, aa
CALL NZ, aa
CALL C, aa
CALL NC, aa
RETURN
RETURN Z
RETURN NZ
RETURN C
RETURN NC 1
JUMP
CALL
RETURN
Address I C A 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
Unconditional
Conditional 1 1
if Zero
if NOT Zero
if Carry
if NOT Carry
Instruction syntax

26. Interrupt Control I C 1 1 INTERRUPT RETURNI Don’t Care Enable Disable
Instruction syntax
INTERRUPT ENABLE
INTERRUPT DISABLE
ENABLE INTERRUPT
DISABLE INTERRUPT 1
INTERRUPT
RETURNI
Don’t Care I C 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
Enable
Disable 1

27. Logical Operation I X Y K C 1 1 LOAD sX, C AND sX, C OR sX, C
LOAD sX, KK
AND sX, KK
OR sX, KK
XOR sX, KK
LOAD sX, sY
AND sX, sY
OR sX, sY
XOR sX, sY C 1
LOAD sX, C
AND sX, C
OR sX, C
XOR sX, C
Constant I X Y K 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
Instruction syntax sX sY 1 K sY

28. Arithmetic Operation I X Y K C 1 1 ADD sX, C ADDCY sX, C SUB sX, C
ADD sX, KK
ADDCY sX, KK
SUB sX, KK
SUBCY sX, KK
ADD sX, sY
ADDCY sX, sY
SUB sX, sY
SUBCY sX, sY C 1
ADD sX, C
ADDCY sX, C
SUB sX, C
SUBCY sX, C
Constant I X Y K 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
Instruction syntax sX sY 1 K sY

29. SHIFT/ROTATE 1 X C D 1 1 SR0/SL0 SR1/SL1 SRX/SLX SRA/SLA RR/RL
SR0 sX
SR1 sX
SRX sX
SRA sX
RR sX
SL0 sX
SL1 sX
SLX sX
SLA sX
RL sX
SR0/SL0
SR1/SL1
SRX/SLX
SRA/SLA
RR/RL 1 1 1
Carry
Instruction 1 X C D 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 sX 1
L - Left
R - Right
Instruction syntax

30. Input/Output Control I X Y P 1 C 1 Input Output Constant PORT_ID sX sY
INPUT sX, PP
INPUT sX, sY
OUTPUT sX, PP
OUTPUT sX, sY 1 C
Input
Output
Constant PORT_ID
Instruction syntax I X Y P 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 sX sY 1 P sY