system on chip (soc)system-on-chip the microprocessor is itself a logic circuit, so it is also...

International semester

2019-2020

Vahid MEGHDADI

System on Chip (SoC)

Vahid MEGHDADI ENSIL-ENSCI Limoges

Course objectifs

Learning how to make cohabit a microprocessor and a logic

circuit.

How to create interface circuit around a µP

Create a simple microprocessor

Add to it input/output ports

Implement all in an FPGA

Assembler PicoBlaze Circuit µP + peripherals

Microprocessor and its peripherals

Some times there are two separate

buses, one from µP to peripherals and

another one from peripherals to µP.

Introduction

System on chip

PicoBlaze a simple soft microprocessor

Declaration et instantiation

Connexion of the memory containing the µP program


Introduction

Typical microprocessor system including some logical circuits around


All on the same integrated circuit (SoC)

System-on-Chip

The microprocessor is itself a logic circuit, so it is also implemented on the

FPGA


FPGA Evolution At the beginning the FPGA contains just some programmable logic,

everything is constructed using them

Memory was then embedded (block RAM)

Hard multipliers are added

Hard core microprocessor was added

« Power PC » for Virtex series,

« Dual-core ARM Cortex » for more recents (7 series)

ADC and DAC are also added


Embedded Microprocessor

Two types of microprocessor

Hard, the µP is burned directly in FPGA

Soft, the µP is just another VHDL program

In the Xilinx FPGA, MicroBlaze is a 32-bit soft µP

In the Xilinx FPGA, PowerPC is a 32-bit hard µP

In the 7-series Xilinx FPGA, ARM Cortex V7-A


Advantage: Creation of tailored µP with

new instruction set (co-processor)

A µP has its own instruction set (addition, subtraction,

jumps, etc.)

One can add more complex instruction (read or send

characters on the serial porta)

These new instructions are implemented in the logical part

of the FPGA

A sub-routine sends the operands into external registers

It waits until the results are ready

It read the results from the registers

Example: sin, cos, complex multiplication, convolution, etc.


Simplified scheme

algorithm

Write the operands to the registers

Wait until the answer is ready

Read the answer


PicoBlaze, a simple « soft-core » µP In this course we construct ore own SoC

We use a simple 8-bit open source µP called PicoBlaze

The VHDL program of the processor is available

There are computer tools who generates the operational code (object code) from assembly language instructions

There are also a tool who creates the VHDL memory component from the object code.

We download this program memory together with the microprocessor and also other logical circuits into the FPGA (using Vivado)


How to use PicoBlaze ?

1. Learn its architecture

2. Learn the instruction set

3. Instantiate the µP component into your own CHDL program

4. Create and connect the program memory to the µP

5. Optionally, add some VHDL code for additional required logic

6. Synthesis, placement and routing the whole ciruit


Architecture of PicoBlaze

Inputs

Outputs

Interface with

program

memory

Inputs Output


Functional example

00xkk

Object

code

Mnemonic

LOAD Sx,kk

Memory

address

000

00ykk’ LOAD Sy,kk’001

10xy0 ADD Sx,Sy002

22aaa JUMP aaa003

000

PC

Init

F8

S5

then003

PC

F2

Sc

kk=06

kk‘=F2

x=5

y=c

aaa=002

06

S5

then001

PC

if code(17 downto 12)=“000000” then

s(code(11 downto 8)) <= code (7 downto 0)

06

S5

then002

PC

F2

Sc

002

PCif code(17 downto 12)=“100010” then

PC <= code(11 downto 0);


VHDL Instantiation

You should declare two

components in your

program.


PicoBlaze declaration in the main

programTwo steps to use the µP: 1) declaration of the component 2) instantiation

Declaration in the declarative zone (before begin)


Instantiation

Max 105 MHz for

Spartan 6PicoBlaze

ports.The signals that

should be declared in

the main program.

Configuration

parameters

Two steps to use the µP: 1) declaration of the component 2) instantiation


Memory declaration and instantiation

Configuration

parameters

PicoBlaze

ports.

The signals that

should be declared in

the main program.


Memory program creation

How to synthesize the program memory and other logical circuit at

the same time?

Write the assembly program in a text file

Create the object codes using the compiler

Create a VHDL program that synthesizes a read-only-memory

(ROM) that contains the object codes

Instantiate the memory and the remaining logic at the same

time


Example : a whole µP circuit Create a simple application : a chaser (Погоня)

All the circuit is created inside the FPGA

Hardware

Write 0x01 in the register S4

Write S4 on the peripheral bus

Rotate right s4

Temporize

Software


Entity

entity test_pico6 is

Port ( CLK : in STD_LOGIC;

LED : out STD_LOGIC_VECTOR(7 downto 0));

end test_pico6;

CLK LED8


PicoBlaze Component Declarationcomponent kcpsm6

generic( hwbuild : std_logic_vector(7 downto 0) := X"00";

interrupt_vector : std_logic_vector(11 downto 0) := X"3FF";

scratch_pad_memory_size : integer := 64);

port ( address : out std_logic_vector(11 downto 0);

instruction : in std_logic_vector(17 downto 0);

bram_enable : out std_logic;

in_port : in std_logic_vector(7 downto 0);

out_port : out std_logic_vector(7 downto 0);

port_id : out std_logic_vector(7 downto 0);

write_strobe : out std_logic;

k_write_strobe : out std_logic;

read_strobe : out std_logic;

interrupt : in std_logic;

interrupt_ack : out std_logic;

sleep : in std_logic;

reset : in std_logic;

clk : in std_logic);

end component;


Memory Component Declaration

component prog_memo

generic ( C_FAMILY : string := "S6";

C_RAM_SIZE_KWORDS : integer := 1;

C_JTAG_LOADER_ENABLE : integer := 0);

Port ( address : in std_logic_vector(11 downto 0);

instruction : out std_logic_vector(17 downto 0);

enable : in std_logic;

rdl : out std_logic;

clk : in std_logic);

end component;


µP InstantiationArchitecture ...

...

Begin

processor: kcpsm6

generic map ( hwbuild => X"00",

interrupt_vector => X"3FF",

scratch_pad_memory_size => 64)

port map( address => adr,

instruction => instr,

bram_enable => bram_enable,

port_id => open, --sortie

write_strobe => we,

k_write_strobe => open, --sortie

out_port => data,

read_strobe => open, --sortie

in_port => "00000000", --entrée

interrupt => '0',

interrupt_ack => open, --sortie

sleep => '0',

reset => kcpsm6_reset,

clk => clk);


Memory Instantiation

program_rom: prog_memo

generic map( C_FAMILY => "S6",

C_RAM_SIZE_KWORDS => 1,

C_JTAG_LOADER_ENABLE => 1)

port map( address => adr,

instruction => instr,

enable => bram_enable,

rdl => kcpsm6_reset,

clk => clk);


Writing Realization

Chronogram of the write

operation from PicoBlaze

to the peripheral port

using the instruction:

OUTPUT Sx,pp

process(clk)

begin

if clk'event and clk = '1' then

if we= '1' then

LED <= data;

end if;

end if;

end process;

The VHDL process to catch

the data at the right time

and to write it on the LEDs.


Environnement ISE

Main program


PicoBlaze instruction set


Exercise (use the PicoBlaze instruction

set) The object codes below represent a program. Find the assembly

program

Run the code. What is the result?

Adresse Code

000 01102

001 01201

002 10120

003 19101

004 32006

005 22002

006 22006

system on chip (soc)system-on-chip the microprocessor is itself a logic circuit, so it is also...

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