Synthesizing and Testing LEON on ADMXRC

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Synthesizing and Testing LEON on ADM-XRC

• Anup Gangwar
• Embedded Systems Group
• Department of Computer Science Engineering
• IIT Delhi

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Presentation Outline

• Introduction
• LEON processor architecture and development
  toolkit
• ADM-XRC board architecture
• Why it took so long?
• Interfacing ZBT SRAM
• Building external hardware interface
• Booting LEON
• From here
• Acknowledgements

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Introduction

• What is LEON?
• A Sparc V8 compliant soft processor core
• No support for paging
• Has been synthesized and tested on many FPGA
  platforms
• Mainly written by Jiri Gaisler at European Space
  Agency
• Supporting toolkit (compiler, assembler,
  simulator) available
• RTEMS successfully ported to LEON with support
  for n/w interface
• How is this relevant to our work?
• Real performance/cost nos. give valuable feedback
  to our tools
• Prototyping adds credibility to our work
• System design experience lets us identify new
  problems
• Working demonstrations help motivate new people

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Presentation Outline

• Introduction
• LEON processor architecture and development
  toolkit
• ADM-XRC board architecture
• Why it took so long?
• Interfacing ZBT SRAM
• Building external hardware interface
• Booting LEON
• From here
• Acknowledgements

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The LEON Processor Architecture
FPU
LEON IU
PCI
Co-Proc
AHB Controller
I-Cache
D-Cache
User I/O
AMBA AHB
AHB/APB Bridge
Timers/UARTs/ I/O Ctrl/IRQ Ctrl
Memory Controller
AMBA APB
PROM/RAM/ I/O
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LEON Development Tools Suite
C-Code
RTEMS Library
GCC - Ported GNU Cross Compiler System
TSIM - LEON Functional Simulator
Modify C Code
N
Performance and Functionality Okay?
Y
ObjCopy - Ported GNU Binutils System
SREC File - Containing Stripped Relocatable
Symbols
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Motorola S-Records Format

• Slttypegtltlengthgtltaddressgtltdata....gtltchecksumgt
• type gt in the range 1-7
• length gt length of (address data checksum)
  in hex
• address gt 4-6 hex characters (16-32 bit
  address)
• data gt each hex pair represents one memory byte
• S3 gt data record with 32-bit addresses
• S7 gt Ending record for S3 records, address is
  the jump address for starting execution

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Presentation Outline

• Introduction
• LEON processor architecture and development
  toolkit
• ADM-XRC board architecture
• Why it took so long?
• Interfacing ZBT SRAM
• Building external hardware interface
• Booting LEON
• From here
• Acknowledgements

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ADM-XRC Architecture
RAM0
RAM1
RAM2
RAM3
Clock Gen.
XCV800-BG560-6
34 I/O pins on SCSI-II style connector
PLX 9080
ADM-XRC
HOST PCI Bus
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ADM-XRC Software API

• Supported platforms are GNU-Linux and Windows NT
• API Supports
• Functions for configuring the Virtex device over
  PCI
• DMA mode for data transfer from/to PLX-9080
• Both master/slave mode supported for PLX-9080
• Examples demonstrate
• Simple PCI interface
• RAM interface with address space segregation
• DMA Master and slave interfaces
• External I/O interfaces

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Presentation Outline

• Introduction
• LEON processor architecture and development
  toolkit
• ADM-XRC board architecture
• Why it took so long?
• Interfacing ZBT SRAM
• Building external hardware interface
• Booting LEON
• From here
• Acknowledgements

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Why it took so long?

• Inability to comprehend the problem properly
• Improper documentation of ZBT memory interface
• Improper methodology for prototyping and testing
• Synthesis being used as testing vehicle which is
  incorrect
• After thorough simulation synthesis should be a
  one-shot process unless the synthesis tools are
  buggy
• External H/W interface was incorrect
• Unnecessary additional logic inversion
• Position of Rx and Tx in 9-pin and 25-pin
  connectors is interchanged
• LEON and memory address lines were not properly
  mapped
• LEON address lines select individual bytes!
• Memory word is 32 bits here hence LEON A10
  need to be left free

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Presentation Outline

• Introduction
• LEON processor architecture and development
  toolkit
• ADM-XRC board architecture
• Why it took so long?
• Interfacing ZBT SRAM
• Building external hardware interface
• Booting LEON
• From here
• Acknowledgements

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Galvantech ZBT SRAM Interface Signals
LEGEND
Galvantech 512K x 36bits
CLK
CKE
CE
OE
R/W
ADV/LD
BWa-d
Address
Data
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ZBT SRAM Read Timing Diagram
CLK
OE
ADV/LD
DONT CARE
R/W
DONT CARE
Address
Data
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ZBT SRAM Write Timing Diagram
CLK
DONT CARE
OE
ADV/LD
DONT CARE
R/W
DONT CARE
Address
Data
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LEON SRAM Read Timing Diagram
CLK
RAMOEN
RAMSN
Address
Data
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LEON SRAM Write Timing Diagram
CLK
RWEN
RAMSN
Address
Data
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Presentation Outline

• Introduction
• LEON processor architecture and development
  toolkit
• ADM-XRC board architecture
• Why it took so long?
• Interfacing memory
• Building external hardware interface
• Booting LEON
• From here
• Acknowledgements

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External Hardware Interface

• Why is external hardware circuitry needed?
• Virtex SelectIOTM supports PCI3.3, LVTTL etc.
  logic levels
• RS-232C voltage conversion required for TxD and
  RxD pins
• Choices for interface chips
• Motorola MC1488/1489
• Require dual supply, 5V, 12V
• Better noise immunity but bigger circuitry
• LVTTL to RS232C and RS232C to LVTTL requires two
  chips
• Maxim Max232
• Single power supply, 5V
• Each chip contains two RS232C to LVTTL and two
  LVTTL to RS232C converters
• Lesser noise immunity but more compact circuitry

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H/W Interface Board Layout
MAX 232 (RS-232C voltage level converters)
Host serial port connections
15 I/O connections from ADM-XRC mapped here
Supporting Circuitry
Power Supply
Probe Points
Power LED
Error LED
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Presentation Outline

• Introduction
• LEON processor architecture and development
  toolkit
• ADM-XRC board architecture
• Why it took so long?
• Interfacing memory
• Building external hardware interface
• Booting LEON
• From here
• Acknowledgements

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Boot Configuration
ADM-XRC
Onboard ZBT SSRAMs used as LEON RAMs
RAM0
RAM1
RAM2
RAM3
H/W Interface Board
Xilinx Virtex XCV800-BG560-6 (virtex_2k_2k_blockpr
om)
Errorn, Resetn, UART1 and UART2 ports mapped to
34 I/O pins for interface
BlockRAMs containing boot-prom, Register Files,
Caches etc (These are instantiated not inferred)
PLX9080
Host PCI Bus (Used for configuring Virtex)
Host Serial Port - 1 (stdin/stdout)
Host Serial Port - 2 (UNIX File Descriptors 2 3)
Host Computer
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Presentation Outline

• Introduction
• LEON processor architecture and development
  toolkit
• ADM-XRC board architecture
• Why it took so long?
• Interfacing memory
• Building external hardware interface
• Booting LEON
• From here
• Acknowledgements

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From Here

• Small Scope Projects
• Try various hardware synthesis configurations for
  LEON
• Build S/W and H/W estimator models for LEON
• Medium Scope Projects
• Build a host of coprocessors for LEON
• Test some PCI cards with LEON-PCI
• Port some real applications to LEON-RTEMS
• Build Ethernet interface for LEON (RTEMS support
  is already present)
• Large Scope Projects
• Extend LEON configuration for multiprocessors
• Customize RTEMS for a particular application/LEON
  configuration

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Presentation Outline

• Introduction
• LEON processor architecture and development
  toolkit
• ADM-XRC board architecture
• Why it took so long?
• Interfacing memory
• Building external hardware interface
• Booting LEON
• From here
• Acknowledgements

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Acknowledgements

• Main ideas, motivation and support
• Prof. M. Balakrishnan and Prof. Anshul Kumar
• Co-Proc interface, Local Bus interface, Bugs in
  memory interface
• Amarjeet Singh
• Debugging, Memory interface, External RS-232C
  hardware interface circuitry
• Amit Aggarwal, Puneet Wadhawan

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Thank You