Double buffer SDRAM Memory ControllerDouble buffer SDRAM Memory Controller

Presented by:

Yael Dresner

Andre Steiner

Instructed by:

Michael Levilov

Project Number: D0713

Project DescriptionProject Description

• Implementation of a device that receives a

grayscale bit map video stream from a digital video

camera, performs a simple pixel processing and

transfers it to a CPU through a double buffer

SDRAM memory.

Blocks DiagramBlocks Diagram

Pixel Processing

Unit

SDRAM controller write part

SDRAM controller read part

Data Bus

Control signal

CPU FPGA CAMERA

Sync

FIFOSwitch

SDRAM A

SDRAM B

Camera ModuleCamera Module• This module is implemented by a test-bench process, which

simulates a digital video camera.

Test BenchTest Bench

synch

Clock – 100MHz

reset

Pixels Data

1024 pixels * t clock period

2 us interval between lines

Start pulse

Pixel Processing ModulePixel Processing Module

synch

clock

reset

Pixels DataProcessed Pixels Data

synch

Simple image

processing

Write Controller ModuleWrite Controller Module

synch

clock

reset

Pixels Data

Control

Addresses Data Path

Input Data

Moore

State Machine

Start pulse

Write Controller ModuleWrite Controller Module

Initialization Write full page Refresh

Write Controller ModuleWrite Controller ModuleWrite Algorithm

• The data is sent to the Sdram block and switched to the Sdram memory which is not used for reading. The switching is done by a different unit in the read controller.

• The data is written to the memory in Full-Page mode (bursts of 1024 bytes).

• One bank is used (out of four).

• Refresh cycles are being done in the time interval between lines.

Switching DiagramSwitching Diagram

SDRAM controller write part

SDRAM controller read part

Switch

SDRAM ASDRAM B

Write Controller ModuleWrite Controller ModuleRefresh Algorithm

• One refresh cycle : 80ns (8 clock periods)

• Time interval between 2 lines : 2us

• 2us/80ns = 25 refresh cycles

• In order to refresh all the 4096 lines we need 4096/25 (163.84) time intervals

• Refreshing the whole memory takes 163.84*(2us + 1024*10ns) = 2msec

• Each line should be refreshed every 64 msec

Cpu ModuleCpu Module• This module is implemented by a test-bench process,

which simulates a Cpu.

• The Cpu asks for the data pixels randomly, using the

“RD” control line.

• The Cpu reads bursts of bytes from the fifo, after

receiving a “RDY” control line. The burst length is set

randomly for each request.

Handling Cpu RequestHandling Cpu Request

Test BenchTest Bench

Pixels Data

RD

RDY

Cpu Clock -100MHz

FIFOFIFO

Read Part

Write Part

SYNCH MODULESYNCH MODULERead Read

ControllerController

RD

RDY

read write

Sdram Clock

Read Controller ModuleRead Controller Module

Read Controller Responsibilities

• Handling The switching between Sdrams

• Reading from Sdram and writing to fifo

• Refreshing

• Handling Cpu requests & reading data from FIFO to Cpu

Read Controller ModuleRead Controller ModuleReading from Sdram algorithm

• The read controller ensures that the FIFO is always full.

• The read controller keeps 2 pointers:

• The address from which reading should continue

• The address which once accessed, switching should occur. This is the last address of data that was written before the previous switching.

Read Controller ModuleRead Controller ModuleRefreshing algorithm

• The read controller is responsible for the refreshing of the Sdram that is currently switched for reading.

• Refreshing all Sdram lines should be done every 64 ms. This process takes 4096*80ns=0.33ms

• during this time the data is not transferred to the FIFO.

Read Controller ModuleRead Controller ModuleSwitching algorithm

• Switching is done after:

• The last address of data that was written is read to the FIFO

• Time interval between lines and refreshing of the write controller is done

• Before switching the write controller stores the last address of written data and sends it to the read controller

Read Controller ModuleRead Controller Module

Switching Unit

Fifo Handling unit

Reading from Sdram Unit

Switch

SDRAM B SDRAM A

FIFOControl & AddressControl

Alternative Write AlgorithmAlternative Write Algorithm

Full page mode Burst mode

1 bank 4 banks

Less complicated implementation of the

write & read controllers

More complicated implementation of the

write & read controllers

Time ScheduleTime Schedule• Implementing the camera test-bench module

• Implementing the pixel processing unit

• Implementing the write part of the SDRAM (Initialization, writing and refreshing)

• Implementing the Cpu Test Bench – One week

• Implementing the fifo and sync module – One week

• Implementing the read controller –Two weeks

• Integration and testing – Two weeks

• learning synthesys and PLACE&ROUTE" tools – Two weeks

• Documentation