RAM 7.0 Betriebsanweisung PDF herunterladen (Seite 29)

DS512 March 1, 2011 www.xilinx.com 29

Product Specification

LogiCORE IP Block Memory Generator v6.1

is made up of AW

, AW

, and AW

. In the same way, BR

is made up of AR

and AR

, and

is made up of BR

and BR

. In the example above, the largest data width ratio is port B Write

words (256 bits) to port A Read words (16 bits); this ratio is 16:1.

Aspect Ratio Limitations

In general, no port data width can be wider than 1152 bits, and no two data widths can have a ratio

greater than 32:1. However, the following optional features further limit data width aspect ratios:

• Byte-writes. When using byte-writes, no two data widths can have a ratio greater than 4:1.

• Fixed primitive algorithm. When using the fixed primitive algorithm with an N-bit wide

primitive, aspect ratios are limited to 32:N and 1:N from the port A Write width. For example,

using the 4kx4 primitive type, the other ports may be no more than 8 times (32:4) larger than port

A Write width and no less than 4 times (1:4) smaller.

Byte-Writes

The Block Memory Generator provides byte-Write support in Kintex-7, Virtex-7, Virtex-6, Virtex-5,

Virtex-4, Spartan-6, and Spartan-3A/3A DSP devices. Byte-writes are available using either 8-bit or 9-

bit byte sizes. When using an 8-bit byte size, no parity bits are used and the memory width is restricted

to multiples of 8 bits. When using a 9-bit byte size, each byte includes a parity bit, and the memory

width is restricted to multiples of 9 bits.

When byte-writes are enabled, the

WE[A|B] (WEA or WEB) bus is N bits wide, where N is the number

of bytes in

DIN[A|B]. The most significant bit in the Write enable bus corresponds to the most

significant byte in the input word. Bytes will be stored in memory only if the corresponding bit in the

Write enable bus is asserted during the Write operation.

When 8-bit bytes are selected, the DIN and DOUT data buses are constructed from 8-bit bytes, with no

parity. When 9-bit bytes are selected, the DIN and DOUT data buses are constructed from 9-bit bytes,

with the 9th bit of each byte in the data word serving as a parity bit for that byte.

The byte-Write feature may be used in conjunction with the data width aspect ratios, which may limit

the choice of data widths as described in Data Width Aspect Ratios, page 27. However, it may not be

used with the NO_CHANGE operating mode. This is because if a memory configuration uses multiple

primitives in width, and only one primitive is being written to (using partial byte writes), then the

NO_CHANGE mode only applies to that single primitive. The NO_CHANGE mode does not apply to

the other primitives that are not being written to, so these primitives can still be read. The byte-Write

feature also affects the operation of WRITE_FIRST mode, as described in Write First Mode

Considerations, page 30.

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