28F640W30 NUMONYX [Numonyx B.V], 28F640W30 Datasheet - Page 85

• Manufacturer Part Number: 28F640W30
• Description: Numonyx Wireless Flash Memory (W30)
• Manufacturer: NUMONYX [Numonyx B.V]

Numonyx™ Wireless Flash Memory (W30)
14.8
14.9
14.10
November 2007
Order Number: 290702-13
Clock Edge (RCR[6])
Configuring the valid clock edge enables a flexible memory interface to a wide range of
burst CPUs. Clock configuration sets the flash device to start a burst cycle, output data,
and assert WAIT on the rising or falling edge of the clock.
Burst Wrap (RCR[3])
The burst wrap bit determines whether 4-word, 8-word, or 16-word burst accesses
wrap within the burst-length boundary, or they cross word-length boundaries to
perform linear accesses.
No-wrap mode (RCR[3]=1) enables WAIT to hold off the system processor, as it does in
the continuous burst mode, until valid data is available.
In no-wrap mode (RCR[3]=0), the flash device operates similarly to continuous linear
burst mode, but consumes less power during 4-word, 8-word, or 16-word bursts.
For example, if RCR[3]=0 (wrap mode) and RCR[2:0] = 1h (4-word burst), possible
linear burst sequences are 0-1-2-3, 1-2-3-0, 2-3-0-1, 3-0-1-2.
If RCR[3]=1 (no-wrap mode) and RCR[2:0] = 1h (4-word burst length), then possible
linear burst sequences are 0-1-2-3, 1-2-3-4, 2-3-4-5, and 3-4-5-6. RCR[3]=1 not only
enables limited non-aligned sequential bursts, but also reduces power by minimizing
the number of internal read operations.
Setting RCR[2:0] bits for continuous linear burst mode (7h) also achieves the above 4-
word burst sequences. However, significantly more power might be consumed. The 1-
2-3-4 sequence, for example, consumes power during the initial access, again during
the internal pipeline lookup as the processor reads word 2, and possibly again,
depending on system timing, near the end of the sequence as the flash device pipelines
the next 4-word sequence. RCR[3]=1 while in 4-word burst mode (no-wrap mode)
reduces this excess power consumption.
Burst Length (RCR[2:0])
The burst length is the number of words the flash device outputs in a synchronous read
access. 4-word, 8-word, 16-word, and continuous-word are supported.
In 4-word, 8-word, or 16-word burst configuration, the burst wrap bit (RCR[3])
determines whether burst accesses wrap within word-length boundaries, or they cross
word-length boundaries to perform a linear access.
After an address is specified, the flash device outputs data until it reaches the end of its
burstable address space. Continuous burst accesses are linear only (burst wrap bit
RCR[3] is ignored during continuous burst) and do not wrap within word-length
boundaries (see
Table 30, “Sequence and Burst Length” on page
84).
Datasheet
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