Introduction to Experiment 7

Replacing Hardwired Control Unitwith the Picoblaze Microcontroller

ECE 448Spring 2009

2ECE 448 – FPGA and ASIC Design with VHDL

Sources

• P. Chu, FPGA Prototyping by VHDL Examples

Chapter 14, Picoblaze Overview Chapter 15, Picoblaze Assembly Code Development Chapter 16, Picoblaze I/O Interface Chapter 17, Picoblaze Interrupt Interface

SSD1SSD2LED

JOYSTICK

PRNG_STATUSPRNG_CTRL

OUTPUT_INTERFACE

INPUT_INTERFACE

PRNGADDR_DECODER

DATARAM

PICOBLAZE

INSTRUCTIONRAM

MEM_BANK

DO[7..0]

DI[7..0]

out_port

A[8..0]

DO[0] A[8]

port_id

A[7..0]

instruction address

addrA[7..0]

RA[7..0]

din

read_strobewrite_strobe

dout

iomem

rng

io, mem, rngSSD1_en, SSD2_enLED_en, MEM_BANK_en,PRNG_CTRL_en,RAM_wen,RAM_ren

we

re

RAM_wen

RAM_ren

in_port

interrupt

interrupt_ack

Two 7-segmentdisplays

8 LEDs

joystick

A[8..0]RD[7..0]

R_wen

R_wen

rinit

rinit

rinit

000001002

. . .

0FE0FF100101102103104105

. . .

1FE1FF

255 x 8 DATARAM

MEM_BANKJOYSTICK

SSD1

SSD2LED

PRNG_STATUSPRNG_CTRL

MEM_BANK

MEM_BANK:

7 6 5 4 3 2 1 0A8

A8 – current memory bank number = the most significant bit of the address

JOYSTICK:

7 6 5 4 3 2 1 0A

A – joystick active (bit cleared by reading registerJOYSTICK or by interrupt_ack),

RLDUS

R, L, D, U, S – joystick right, left, down, up, select

PRNG_STATUS:

7 6 5 4 3 2 1 0D

D – done: bit cleared by writingto register PRNG_CTRL, set after PRNGgenerates 255 8-bit numbers,

PRNG_CTRL:

7 6 5 4 3 2 1 0I

I – initialize: after 1 is written to this bit,PRNG generates 255 8-bit numbers, and the corresponding address (index) of each number

Task 1 – Browsing Mode

00 0102030405….

FAFBFCFDFE

00 0102030405….

FAFBFCFDFE

Address Data

Current Address Two 7-SegmentDisplays

(in hexadecimalnotation)

Joystick up = Increment Address

Joystick down = Decrement Address

8 LEDs(in binarynotation)

Value at Current Address

255x8 RAM

Task 2 – Edit Mode

00 0102030405….

FAFBFCFDFE

00 01020304

05=>06….

FAFBFCFDFE

Address Data

Current Address Two 7-SegmentDisplays

(in hexadecimalnotation)

Joystick up = Increment Address

Joystick down = Decrement Address

8 LEDs(in binarynotation)

Value at Current Address

255x8 RAM

Joystick Enter = Edit

Joystick up = Increment Data

Joystick down = Decrement Data

Joystick Enter = Approve

Task 3 – Initialize

00 0102030405….

FAFBFCFDFE

25 879426B5C6….

7A5B344389

Address Data

Joystick Enter = Initialize with Pseudorandom Values

255x8 RAM

8-bit LFSR (Linear Feedback Shift Register)with the period of 28-1

8

R

R0R1R2R3R4R5R6R7

= D flip-flop with set or reset determining its initialvalue after “soft” reset

Run for 8 clock cycles before using a new output value.

Task 4 – Sorting

00 0102030405….

FAFBFCFDFE

25 3744565778….

B4B6B8CCD4

Address Data

Joystick Enter = sorting using one of the following types

sorting signed numbers in the descending ordersorting signed numbers in the ascending ordersorting unsigned numbers in the descending ordersorting unsigned numbers in the ascending order

Joystick Up changing sorting type

255x8 RAM

Task 5 – Advanced Testbench

ProcessesGenerating

InputStimuli

Design Under Test (DUT)

ProcessComparing

Actual Outputs

vs.Expected

Outputs

DesignCorrect/Incorrect

Yes/NoTestvector

file(s)

Task 5 – Format of an input file

number of entries to be sorted (in decimal)empty line

numbers to be sorted in the initial order (in the hexadecimal notation, one number per line)

empty line

numbers after sorting (in the hexadecimal notation, one number per line)

6

B489A3586178

58617889A3B4

Task 6 : Comparing Circuits from

Experiment 6 and Experiment 7(hardwired vs. Picoblaze-based

controller) in terms of

• minimum number of clock cycles necessary to complete sorting• minimum clock period• resource utilization.

Introduction to Picoblaze Development Environment

(Hands-on Session)