Embedded Memory (RAM: 1-PORT, RAM: 2-PORT, ROM: 1-PORT, and ROM: 2-PORT) User Guide

ID 683240
Date 9/17/2021
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3.4. Mixed-width Port Configuration

Only dual-port RAM and dual-port ROM support mixed-width port configuration for all memory block types except when they are implemented with LEs. The support for mixed-width port depends on the width ratio between port A and port B. In addition, the supporting ratio varies for various memory modes, memory blocks, and target devices.
Note: MLABs do not have native support for mixed-width operation, thus the option to select MLABs is disabled in the parameter editor. However, the Intel® Quartus® Prime software can implement mixed-width memories in MLABs by using more than one MLAB. Therefore, if you select AUTO for your memory block type, it is possible to implement mixed-width port memory using multiple MLABs.

Memory depth of 1 word is not supported in simple dual-port and true dual-port RAMs with mixed-width port. The parameter editor prompts an error message when the memory depth is less than 2 words. For example, if the width for port A is 4 bits and the width for port B is 8 bits, the smallest depth supported by the RAM is 4 words. This configuration results in memory size of 16 bits (4 × 4) and can be represented by memory depth of 2 words for port B. If you set the memory depth to 2 words that results in memory size of 8 bits (2 × 4), it can only be represented by memory depth of 1 word for port B, and therefore the width of the port is not supported.