Lecture 7 Lecture 7: Hardware/Software Systems on the XUP Board ECE 412: Microcomputer Laboratory

Lecture 7

Lecture 7: Hardware/Software Systems on the XUP Board

ECE 412: Microcomputer Laboratory

Lecture 7

Outline• Overview of Linux/HW interaction on the XUP board• Resources available for you on the board• Discussion of the Virtex-II Pro’s BlockRAMs

Lecture 7

Review Questions• What function does the mmap() call serve in

implementing memory-mapped I/O?

• What are the two alternatives of communicating between the devices and the processor? Comparison of these methods?

Lecture 7

Review Questions• What function does the mmap() call serve in implementing

memory-mapped I/O?– mmap() causes a set of device registers or other data to be

mapped onto a region in the address space

• What are the two alternatives of communicating between the devices and the processor? Comparison of these methods?– Polling:

• takes CPU time even if no requests pending• can be better if the processor has nothing better to do and has to

respond to an event ASAP

– Interrupts: • no overhead when no requests pending• can be better if the processor has other work to do and the time to

respond to events isn’t absolutely critical (need context switching)

Lecture 7

The XUP BoardXUP BoardFPGA

PowerPCPowerPC

I/O ConnectorI/O Connector I/O ConnectorI/O Connector

SDRAMSDRAM

EthernetEthernet

Serial PortSerial Port

Audio In/OutAudio In/Out

VGAVGA

FLASH CardFLASH Card

Lecture 7

Pure-Hardware SystemXUP BoardFPGA

PowerPCPowerPC


Logic

SDRAMSDRAM

EthernetEthernet



VGAVGA


Lecture 7

XUP Board as PCXUP BoardFPGA

PowerPCPowerPC


EthernetEthernet

SDRAMSDRAM



VGAVGA

FLASH CardFLASH CardFLASH ControllerFLASH Controller

VGA ControllerVGA Controller

Audio ControllerAudio Controller

UART ControllerUART Controller

Ethernet ControllerEthernet Controller

SDRAM ControllerSDRAM Controller

PLB Bus

Lecture 7

ECE 412 Approach -- HW/SW SystemXUP BoardFPGA

PowerPCPowerPC


EthernetEthernet

SDRAMSDRAM



VGAVGA

FLASH CardFLASH CardFLASH ControllerFLASH Controller



PLB BusLogicLogic

Lecture 7

MP2 ConfigurationXUP BoardFPGA

PowerPCPowerPC

I/O ConnectorI/O Connector

EthernetEthernet

SDRAMSDRAM



VGAVGA

FLASH ControllerFLASH Controller



PLB BusLogicLogic

Core

Core OPB

I/O ConnectorI/O Connector


Lecture 7

Embedded Power PC 405 Core

Lecture 7

PPC• Functional blocks

– Cache units (ICU and DCU, 16 KB each)– Memory Management unit– Fetch Decode unit– Execution unit– Timers– Debug logic unit

• It operates on instructions in a five stage pipeline consisting of – fetch, decode, execute, write-back, and load write-back– Most instructions execute in a single cycle, including loads

and stores.

Lecture 7

Creating a HW/SW System• Custom logic needs to conform to bus/interface

protocols– We’ll provide documentation about this– For MP2.1, we provide a prototype for the function you have

to write (In VHDL)

• Assemble custom logic, IP cores, software into a package that can be downloaded onto the board– EDK tool creates bit file for FPGA– SystemACE HW loads Linux/other SW off of FLASH card– Can also pre-load BlockRAMs w/data as part of FPGA

programming

Lecture 7

Interfaces to the PowerPC Cores• Processor Local Bus (PLB)

– 64-bit bus that handles fast data transfers with the PowerPC and the peripherals

• For example, DDR controller hangs on this bus• There is also a 32-bit bus called OPB (On-Chip Peripheral Bus)

that handles slower peripheral devices• For example, for UART and SystemACE access• Needs to connect to PLB via a special PLB-to-OPB bridge

• OCM (On-Chip Memory) Controller– Allows memory (BlockRAMs) to be accessed at rates comparable

to the caches– Great way to build data buffers

• Interrupt Controller• Device Control Register

– Allows creation of a register file that is “shared” among all of the devices connected to the PowerPC

• Clock, Power Management• JTAG Port

Lecture 7

Other Resources• SDRAM

– Lots of space, complex interface requirements– Controlled via IP core– Your HW can interface with core, simplifying things

• BlockRAM– Small, on-chip memory– Can be configured in a number of ways– Fast, simple interface

Lecture 7

Virtex Block SelectRAM• 18Kb capacity and configurable at build time to be either:

1 x 16K

2 x 8K

4 x 4K

8 x 2K

16 x 1K

32 x 512

• 136 of these on each XC2VP30 FPGA for total of 2.4Mb total

• Dual ported, can be aggregated to form larger structures

• Parity bits, possible to pre-load with data in VHDL

Lecture 7

Generic Block Diagrams

Lecture 7

Interface Signals

Lecture 7

Supported Configurations

• Your VHDL will instantiate using primitives• Each reference is an individual BRAM• Could form larger memory block by assembling number of

primitives, routing delay would determine total access time.

Lecture 7

Physical Location

Lecture 7

Read and Write TimingRefer to posted application notes for exact details:• XAPP-463 (says Spartan-3 but is applicable to our parts)• XAPP-130 (basic operation, but is for early smaller BRAMS)

Lecture 7

Instantiating BlockRAMs• Declare as components, can instantiate multiple

copies of a component

component RAMB16_s9

Port ( clk : in std_logic; ... );

end component;

• Documentation section of the web page has instructions on simulating designs that use BlockRAM, example that links multiple BlockRAMs to form larger memory

Lecture 7

Uses for BlockRAMs• “Scratchpad” memories in designs• ROM arrays -- can pre-load BlockRAMs with fixed

values– CLBs are reasonably efficient at implementing ROMs, so

don’t need to use BlockRAMs unless you have a very big ROM

– CLB’s are very inefficient at implementing RAMs, want to use a BlockRAM any time you need more than a few words of RAM/register

• Buffer for Linux/HW communication– One simple way to move data between Linux and HW is to

use BlockRAM buffer for data, interrupt/register write to signal when data is ready.

Lecture 7

Next Time• The PLB bus

Documents

Lecture 7 Lecture 7: Hardware/Software Systems on the XUP Board ECE 412: Microcomputer Laboratory