OCP-based memory access arbitration for a digital sampling oscilloscope

By Traian Tulbure and Dan Nicula, eASIC
Programmable Lgic Designline

The current approach for designing an integrated circuit in the form of a System-on-Chip (SoC) is based on reusing the models for modules with a well-defined functionality. For easier interconnection, these intellectual property (IP) cores should have an interface that obeys the rules of a standard socket.

The Open Core Protocol (OCP) is a common standard for IP core interfaces, or sockets, which facilitates the concept of "plug and play" design for SoCs. This paper presents the use of the OCP with regard to implementing a multi-port access memory with a single port SRAM. The study case is a digital sampling oscilloscope (DSO) implemented on a FlexASIC device from eASIC. The general capabilities of the chip include a two-channel digital sampling DSO and an arbitrary waveform generator (AWG) in a single USB-powered module.

The chip is implemented on Structured eASIC fabric that includes single port SRAM blocks. The on-chip SRAM is shared between the DSO and the AWG. Furthermore, the CPU also requires access to the memory; thus, a time-multiplexed memory access subsystem was designed. The OCP protocol was chosen to provide access and arbitration of the SRAM access on a 96 bit wide data bus.

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