Datasheet

DS1972
1024-Bit EEPROM i
Button
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Memory Access
Data memory and registers are located in a linear
address space, as shown in Figure 5. The data memory
and the registers have unrestricted read access. The
DS1972 EEPROM array consists of 18 rows of 8 bytes
each. The first 16 rows are divided equally into four
memory pages (32 bytes each). These four pages are
the primary data memory. Each page can be individu-
ally set to open (unprotected), write protected, or
EPROM mode by setting the associated protection byte
in the register row. As a factory default, the entire data
memory is unprotected and its contents are undefined.
The last two rows contain protection registers and
reserved bytes. The register row consists of 4 protec-
tion-control bytes, a copy-protection byte, the factory
byte, and 2 user byte/manufacture ID bytes. The manu-
facturer ID can be a customer-supplied identification
code that assists the application software in identifying
the product with which the DS1972 is associated.
Contact the factory to set up and register a custom
manufacturer ID. The last row is reserved for future use.
It is undefined in terms of R/W functionality and should
not be used.
In addition to the main EEPROM array, an 8-byte
volatile scratchpad is included. Writes to the EEPROM
array are a two-step process. First, data is written to the
scratchpad and then copied into the main array. This
allows the user to first verify the data written to the
scratchpad prior to copying into the main array. The
device only supports full row (8-byte) copy operations.
For data in the scratchpad to be valid for a copy opera-
tion, the address supplied with a Write Scratchpad
command must start on a row boundary, and 8 full
bytes must be written into the scratchpad.
ADDRESS RANGE TYPE DESCRIPTION PROTECTION CODES
0000h to 001Fh R/(W) Data Memory Page 0 —
0020h to 003Fh R/(W) Data Memory Page 1 —
0040h to 005Fh R/(W) Data Memory Page 2 —
0060h to 007Fh R/(W) Data Memory Page 3 —
0080h* R/(W) Protection-Control Byte Page 0
55h: Write Protect P0; AAh: EPROM Mode P0;
55h or AAh: Write Protect 80h
0081h* R/(W) Protection-Control Byte Page 1
55h: Write Protect P1; AAh: EPROM Mode P1;
55h or AAh: Write Protect 81h
0082h* R/(W) Protection-Control Byte Page 2
55h: Write Protect P2; AAh: EPROM Mode P2;
55h or AAh: Write Protect 82h
0083h* R/(W) Protection-Control Byte Page 3
55h: Write Protect P3; AAh: EPROM Mode P3;
55h or AAh: Write Protect 83h
0084h* R/(W) Copy Protection Byte
55h or AAh: Copy Protect 0080h:008Fh, and Any
Write-Protected Pages
0085h R Factory Byte. Set at Factory.
AAh: Write Protect 85h, 86h, 87h;
55h: Write Protect 85h; Unprotect 86h, 87h
0086h R/(W) User Byte/Manufacturer ID —
0087h R/(W) User Byte/Manufacturer ID —
0088h to 008Fh — Reserved —
Figure 5. Memory Map
* Once programmed to AAh or 55h this address becomes read only. All other codes can be stored, but neither write protect the
address nor activate any function.