ade7518 Analog Devices, Inc., ade7518 Datasheet - Page 87

• Manufacturer Part Number: ade7518
• Description: Single-phase Energy Measurement Ic With 8052 Mcu, Rtc, And Lcd Driver
• Manufacturer: Analog Devices, Inc.

FLASH MEMORY
OVERVIEW
Flash memory is a type of nonvolatile memory that is in-circuit
programmable. The default state of a byte of flash memory is 0xFF
(erased). When a byte of flash memory is programmed, the
required bits change from 1 to 0. The flash memory must be
erased to turn the 0s back to 1s. However, a byte of flash memory
cannot be erased individually. The entire segment, or page, of
flash memory that contains the byte must be erased.
The ADE7518 provides 16 kB of flash program/information
memory. This memory is segmented into 32 pages of 512 bytes
each. Therefore, to reprogram one byte of flash memory, the
other 511 bytes in that page must be erased. The flash memory
can be erased by page or all at once in a mass erase. There is a
command to verify that a flash write operation has completed
successfully. The ADE7518 flash memory controller also offers
configurable flash memory protection.
The 16 kB of flash memory are provided on-chip to facilitate
code execution without any external discrete ROM device
requirements. The program memory can be programmed in-
circuit, using the serial download or emulation options provided or
using conventional third party memory programmers.
Flash/EE Memory Reliability
The flash memory arrays on the ADE7518 are fully qualified for
two key Flash/EE memory characteristics: Flash/EE memory
cycling endurance and Flash/EE memory data retention.
Endurance quantifies the ability of the Flash/EE memory to be
cycled through many program, read, and erase cycles. In real
terms, a single endurance cycle is composed of the following four
independent, sequential events:
1.
2.
3.
4.
Initial page erase sequence.
Read/verify sequence.
Byte program sequence.
Second read/verify sequence.
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In reliability qualification, every byte in both the program and
data Flash/EE memory is cycled from 0x00 to 0xFF until a first
fail is recorded, signifying the endurance limit of the on-chip
Flash/EE memory.
As indicated in the Specifications section, the ADE7518 flash
memory endurance qualification has been carried out in
accordance with JEDEC Standard 22 Method A117 over the
industrial temperature range of −40°C, +25°C, and +85°C. The
results allow the specification of a minimum endurance figure
over supply and temperature of 100,000 cycles, with a minimum
endurance figure of 20,000 cycles of operation at 25°C.
Retention is the ability of the flash memory to retain its pro-
grammed data over time. Again, the parts have been qualified
in accordance with the formal JEDEC Standard 22 Method A117
at a specific junction temperature (TJ = 55°C). As part of this
qualification procedure, the flash memory is cycled to its specified
endurance limit before data retention is characterized. This
means that the flash memory is guaranteed to retain its data for
its full specified retention lifetime every time the flash memory is
reprogrammed. It should also be noted that retention lifetime,
based on an activation energy of 0.6 eV, derates with T
in Figure 78.
300
250
200
150
100
50
0
40
Figure 78. Flash/EE Memory Data Retention
50
T
J
60
JUNCTION TEMPERATURE (°C)
ANALOG DEVICES
SPECIFICATION
100 YEARS MIN.
AT T
70
J
= 55 ° C
80
90
100
ADE7518
J
, as shown
110