24LC32-/P MICROCHIP [Microchip Technology], 24LC32-/P Datasheet - Page 9

• Manufacturer Part Number: 24LC32-/P
• Manufacturer: MICROCHIP [Microchip Technology]

6.6
The cache is a 64 byte (8 pages x 8 bytes) FIFO buffer.
The cache allows the loading of up to 64 bytes of data
before the write cycle is actually begun, effectively pro-
viding a 64-byte burst write at the maximum bus rate.
Whenever a write command is initiated, the cache
starts loading and will continue to load until a stop bit is
received to start the internal write cycle. The total
length of the write cycle will depend on how many
pages are loaded into the cache before the stop bit is
given. Maximum cycle time for each page is 5 ms. Even
if a page is only partially loaded, it will still require the
same cycle time as a full page. If more than 64 bytes of
data are loaded before the stop bit is given, the address
pointer will'wrap around' to the beginning of cache
page 0 and existing bytes in the cache will be overwrit-
ten. The device will not respond to any commands
while the write cycle is in progress.
6.7
If a write command begins at a page boundary
(address bits A2, A1 and A0 are zero), then all data
loaded into the cache will be written to the array in
sequential addresses. This includes writing across a
4K block boundary. In the example shown below,
(Figure 4-2) a write command is initiated starting at
byte 0 of page 3 with a fully loaded cache (64 bytes).
The first byte in the cache is written to byte 0 of page 3
(of the array), with the remaining pages in the cache
written to sequential pages in the array. A write cycle is
executed after each page is written. Since the write
begins at page 3 and 8 pages are loaded into the
cache, the last 3 pages of the cache are written to the
next row in the array.
2004 Microchip Technology Inc.
PAGE CACHE AND ARRAY MAPPING
Cache Write Starting at a Page
Boundary
6.8
When a write command is initiated that does not begin
at a page boundary (i.e., address bits A2, A1 and A0
are not all zero), it is important to note how the data is
loaded into the cache, and how the data in the cache is
written to the array. When a write command begins, the
first byte loaded into the cache is always loaded into
page 0. The byte within page 0 of the cache where the
load begins is determined by the three least significant
address bits (A2, A1, A0) that were sent as part of the
write command. If the write command does not start at
byte 0 of a page and the cache is fully loaded, then the
last byte(s) loaded into the cache will roll around to
page 0 of the cache and fill the remaining empty bytes.
If more than 64 bytes of data are loaded into the cache,
data already loaded will be overwritten. In the example
shown in Figure 7-2, a write command has been initi-
ated starting at byte 2 of page 3 in the array with a fully
loaded cache of 64 bytes. Since the cache started load-
ing at byte 2, the last two bytes loaded into the cache
will'roll over' and be loaded into the first two bytes of
page 0 (of the cache). When the stop bit is sent, page
0 of the cache is written to page 3 of the array. The
remaining pages in the cache are then loaded sequen-
tially to the array. A write cycle is executed after each
page is written. If a partially loaded page in the cache
remains when the STOP bit is sent, only the bytes that
have been loaded will be written to the array.
6.9
This design incorporates a power standby mode when
the device is not in use and automatically powers off
after the normal termination of any operation when a
stop bit is received and all internal functions are com-
plete. This includes any error conditions, ie. not receiv-
ing an acknowledge or stop condition per the two-wire
bus specification. The device also incorporates V
monitor circuitry to prevent inadvertent writes (data cor-
ruption) during low-voltage conditions. The V
tor circuitry is powered off when the device is in standby
mode in order to further reduce power consumption.
Cache Write Starting at a Non-Page
Boundary
Power Management
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