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3–2 Chapter 3: External Memory BFM

Functional Description

Avalon Verification IP Suite User Guide May 2011 Altera Corporation

Table 3–2 lists the function of the external memory BFM and its related components.

f For more information about tristate conduit bridge, refer to “Tristate Conduit Bridge”

section in the Qsys Interconnect chapter of the Quartus II Handbook.

For more information about tristate conduit pin sharer, refer to “Tristate Conduit Pin

Sharer” section in the Qsys Interconnect chapter of the Quartus II Handbook.

For more information about generic tristate controller, refer to “Generic Tristate

Controller” section in the Qsys Interconnect chapter of the Quartus II Handbook.

Initializing the Memory Content

At the beginning of the simulation, the external memory BFM loads the memory

initialization file (

INIT_FILE

) to initialize its memory content. For example, if the

memory file has a memory size of 50, the BFM fills its memory content with addresses

0–49. However, if you do not provide the memory initialization file, the memory

content of the BFM remains blank.

Reading and Writing to the Memory Content

You can read or write to the memory content through the APIs or the interface signals.

Reading from the Memory

The BFM uses

cdt_data_io

as a bidirectional data port. During read transfers, this

port acts as an output port and drives the corresponding address memory content

when the BFM asserts or deasserts the following signals:

■ Asserts

cdt_output_enable

signal

■ Asserts

cdt_read

signal

■ Deasserts

cdt_write

signal

■ Asserts

cdt_chip_select

signal

Otherwise, the

cdt_data_io

port acts as an inactive input port and is held in high

impedance state.

Table 3–1. External Memory BFM and Related Components

Component Description

External memory BFM

Represents the external RAM. The external memory BFM is a

memory model with an Avalon-TC interface. The BFM also models a

set of memories that are supported by the generic tristate controller

component.

Tristate Conduit Bridge Converts Avalon-TC signals into conduit signals.

Tristate Conduit Pin Sharer

Carries the shared address bus and data.

Tristate Conduit Inverse Pin

Sharer

Generic Tristate Controller

Controls the external memory BFM. The generic tristate controller

accepts read and write requests and converts these requests into

necessary SDRAM and bank management commands.

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