Intel® Agilex™ Embedded Memory User Guide

ID 683241
Date 4/25/2022
Public

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4.3.10. Different Input and Output Width

The DCFIFO_MIXED_WIDTHS function supports different write input data and read output data widths if the width ratio is valid. The FIFO parameter editor prompts an error message if the combinations of the input and the output data widths produce an invalid ratio. The supported width ratio in a power of 2 and depends on the RAM.

The IP core supports a wide write port with a narrow read port, and vice versa. The current supported mixed width ratios for Intel® Agilex™ devices are listed in the following table:

Table 47.  Device Family Support for Width Ratios
Device Family Valid Width Ratio
Intel® Agilex™ 1, 2, 4, 8, 16, and 32
Figure 39.  Writing 16-bit Words and Reading 8-bit WordsThis figure shows an example of a wide write port (16-bit input) and a narrow read port (8-bit output).

In this example, the read port is operating at twice the frequency of the write port. Writing two 16-bit words to the FIFO buffer increases the wrusedw flag to two and the rusedw flag to four. Four 8-bit read operations empty the FIFO buffer. The read begins with the least-significant 8 bits from the 16-bit word written followed by the most-significant 8 bits.

Figure 40. Writing 8-Bit Words and Reading 16-Bit WordsThis figure shows an example of a narrow write port (8-bit input) with a wide read port (16-bit output).

In this example, the read port is operating at half the frequency of the write port. Writing four 8-bit words to the FIFO buffer increases the wrusedw flag to four and the rusedw flag to two. Two 16-bit read operations empty the FIFO. The first and second 8-bit word written are equivalent to the LSB and MSB of the 16-bit output words, respectively. The rdempty signal stays asserted until enough words are written on the narrow write port to fill an entire word on the wide read port.

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