Rainbow Electronics DS1972 - Manual (Page 6)

DS1972: 1024-Bit EEPROM iButton
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Figure 5. Memory Map
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 1) R/(W) Protection Control Byte
Page 0
55h: Write Protect P0; AAh: EPROM mode
P0; 55h or AAh: Write Protect 80h
0081h 1) R/(W) Protection Control Byte
Page 1
55h: Write Protect P1; AAh: EPROM mode
P1; 55h or AAh: Write Protect 81h
0082h 1) R/(W) Protection Control Byte
Page 2
55h: Write Protect P2; AAh: EPROM mode
P2; 55h or AAh: Write Protect 82h
0083h 1) R/(W) Protection Control Byte
Page 3
55h: Write Protect P3; AAh: EPROM mode
P3; 55h or AAh: Write Protect 83h
0084h 1) R/(W) Copy Protection Byte 55h or AAh: Copy Protect 0080:008Fh, 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 N/A Reserved
1) Once programmed to AAh or 55h this address becomes read-only. All other codes can be stored but will neither
write-protect the address nor activate any function.
MEMORY
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 4 memory pages (32 bytes each). These 4 pages are the primary data memory.
Each page can be individually set to Open (unprotected), Write-Protected, or EPROM mode by setting the
associated protection byte in the register row. The last two rows contain protection registers, and reserved bytes.
The register row consists of 4 protection control bytes, a copy protection byte, the factory byte, and two user
byte/manufacture ID bytes. The manufacturer ID can be a customer-supplied identification code that assists the
application software in identifying the product the DS1972 is associated with. 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 scratchpad prior to copying into the main array. The device only supports full
row (8-byte) copy operations. In order for data in the scratchpad to be valid for a copy operation, the address
supplied with a Write Scratchpad must start on a row boundary, and 8 full bytes must be written into the
scratchpad.