DS1982 Maxim, DS1982 Datasheet - Page 7

• Manufacturer Part Number: DS1982
• Description: The DS1982 1Kb Add-Only iButton is a rugged read/write data carrier that identifies and stores relevant information about the product or person to which it is attached
• Manufacturer: Maxim

MEMORY FUNCTION COMMANDS
The “Memory Function Flow Chart” (Figure 6) describes the protocols necessary for accessing the
various data fields within the DS1982. The Memory Function Control section, 8-bit scratchpad, and the
Program Voltage Detect circuit combine to interpret the commands issued by the bus master and create
the correct control signals within the device. A 3-byte protocol is issued by the bus master. It is comprised
of a command byte to determine the type of operation and 2 address bytes to determine the specific
starting byte location within a data field. The command byte indicates if the device is to be read or
written. Writing data involves not only issuing the correct command sequence but also providing a 12-
volt programming voltage at the appropriate times. To execute a write sequence, a byte of data is first
loaded into the scratchpad and then programmed into the selected address. Write sequences always occur
a byte at a time. To execute a read sequence, the starting address is issued by the bus master and data is
read from the part beginning at that initial location and continuing to the end of the selected data field or
until a reset sequence is issued. All bits transferred to the DS1982 and received back by the bus master
are sent least significant bit first.
DS1982 MEMORY MAP Figure 5
ADDRESS:
1024-BIT
EPROM
EPROM STATUS BYTES
0007h
(MSB)
STARTING
ADDRESS
0006h
0040h
0000h
0060h
0020h
0005h
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4-7
8-BIT SCRATCHPAD
Page 7 of 24
0004h
WRITE PROTECT PAGE 0
WRITE PROTECT PAGE 1
WRITE PROTECT PAGE 2
WRITE PROTECT PAGE 3
BITMAP OF USED PAGES (RESERVED FOR TMEX)
32 BYTES
32 BYTES
32 BYTES
32 BYTES
PAGE 0
PAGE 1
PAGE 2
PAGE 3
0003h
0002h
0001h
0000h
(LSB)
DS1982