Design for High-Level Model Based on an Eight Bit Entertainment System Alejandro Lizaola, Ricardo Castro, Gilberto Beltran. Manuel Salim and Alejandro Moreno Departamento de electronica, Systemas e Informatica Instituto Tecnologico y de Estudios Superiores de Occidente Guadalajara, Mexico.

Outline  Introduction  NES Main Block Description  Design Methodology  Verification Strategies  Results  Conclusions 2

Introduction  NES prototype has been developed in order to increase engineering skills on this area.  This one was not verified, formal verification process has not been executed.  Design lifecycle must be complete. 3

…Introduction  A model reference will be developed in a hardware description and verification language.  Design.  Implementation.  Verification.  Validation.  Reverse engineering will help to speed up the knowledge and design of the NES. 4

NES Arquitecture 5

Design Methodology 1. NES functionality understanding. 2. Emulator election. 3. Reference model design. 4. Reference model main blocks implementation. 5. Reference model integration modules. 6

Main Block Description 7 Main Block Proposal:

…Verification Strategies Reference Model Verification: 8

Verification Plan: All functional areas as well as monitors and checkers are described through the specification of the console. Monitor and checkers are used to know the status of :  Memory.  Flags.  I/O Signals.  Variables. Verification Strategies 9

…Results Mapper comparison between output files using Soccer Game ROM. 10 Reference ModelEmulator

Results Triangular channel outputs for Soccer game. 11 Emulator Reference Model Comparison Results

…Results Delta Modulation outputs for Soccer game. 12 Emulator Reference Model Comparison Results

…Results Audio buffer outputs for Soccer game. 13 Emulator Reference Model Comparison Results

…Results Scroll results for Soccer game. Sprites results for Soccer game. 14 Emulator Reference Model Comparison Results Reference Model Emulator

…Results Game’s name Mapper Number Funtionality Comparision Soccer, Demo Sound, Donkey Kong, Súper Mario Bros 10Correct Contra2Correct Castlevania I, Legend of Zelda, Techno Baseball, Road Race, Megaman I, III 1Correct Hudson Island I,II, III3Correct Punch Out9Correct Megaman II3Incorrect Castlevania III Japanese version24Incorrect Súper Mario Bros III5Correct Nintendo World Cup, Tiny Toons, Mitsufatoru4Correct Dragon Ball Z16Incorrect Result table games. 15

Conclusions  NES functionality, interconnection and architecture was developed.  After several attempt to select an PC emulator, NesCore has been selected.  Reference model was implemented in SystemVerilog in a modular way, adding two none existing modules in the NES prototype. 16

…Conclusions  An automated verification strategy was implemented:  Human Factor Reduction.  Improve efficiency.  Faster results comparison.  The performance of the model behaves as expected due to results comparison. 17

Future Work  Mappers and more expansion chips can be implemented.  Verification´s framework must be implemented.  NES prototype verification can be done. 18

Question & Answers… Any question ?

Slides Background Central Processing Unit: The CPU emulated by the NES is an 8-bit microprocessor produced by Ricoh based on MOS Technology 6502 core. The NTSC version (North America and Japan) of the console use the Ricoh 2A03 (or RP2A03), which operates at 1.78MHz, PAL version (Europe and Australia) use the Ricoh 2A07 (or RP2A07), this is identical to version NTSC with the difference that it works on 1.66MHz.

Slides Background Audio Processing Unit: The APU is responsible for generating the game sound. It is implemented in two chips, RP2A03 for NTSC and RP2A07 for PAL. The APU has 5 channels: 1. Square channel, frequency ranges 54 Hz – 28 KHz. 2. Square channel, frequency ranges 54 Hz – 28 KHz. 3. Triangle channel, frequency ranges 27 Hz – 56 KHz. 4. Noise channel, LFSR, two modes and sixteen programmable frequencies. 5. DPCM channel.

Slides Background MAPPERS: Mappers are chips designed for videogames developers to use them in NES cartridges. Mappers are used to access memory beyond the limits of the 64k memory, allowing special effects in the video and sound, such as forcing some interruptions and instructions among other things. The memory used by the NES is implemented in two blocks, Rom program (PRG-ROM) and Rom Character (CHR-ROM). This includes the memory area where the current code will be executed by the micro as well as the video memory data.

Slides Background Picture Processing Unit: The PPU used by the NES was designed by Ricoh. This unit is responsible for transforming the digital information received from the CPU into video signal to display the game on screen. This process is known as image rendering The PPU contains the following: 1. Background render unit. 2. Sprites render unit. 3. Records of entry and exit. 4. Internal RAM 32B. 5. External RAM 256B.