Datasheet
Dual, Temperature-Controlled Resistors with Inter-
nally Calibrated Monitors and Password Protection
Maxim Integrated 11
DS1856
Variable Resistors
The value of each variable resistor is determined by
a temperature-addressed look-up table, which can
assign a unique value (00h to FFh) to each resistor for
every 2°C increment over the -40°C to +102°C range
(see Table 3). See the
Temperature Conversion
section
for more information.
The variable resistors can also be used in manual
mode. If the TEN bit equals 0, the resistors are in man-
ual mode and the temperature indexing is disabled.
The user sets the resistors in manual mode by writing
to addresses 82h and 83h in Table 03 to control resis-
tors 0 and 1, respectively.
Memory Description
The memory of the DS1856 is divided into two areas
referred to as the Main Device and the Auxiliary
Device. The Main Device comprises all of the DS1856
specific memory while the Auxiliary Device consists of
128 bytes of general-purpose EEPROM and is espe-
cially useful in GBIC applications. Main and Auxiliary
ADEN
(ADDRESS
ENABLE)
NO. OF SEPARATE
DEVICE
ADDRESSES
ADDITIONAL
INFORMATION
0 2 See Figure 2
1
1 (Main Device Only)
See Figure 3
Table 4. ADEN Address Configuration
ADEN ADFIX
AUXILIARY
ADDRESS
MAIN ADDRESS
0 0 A0h A2h
0 1 A0h
EEPROM
(Table 03, 8Ch)
1 0 — A2h
11 —
EEPROM
(Table 03, 8Ch)
Table 5. ADEN and ADFIX Bits
AUXILIARY DEVICE
EEPROM
AUXILIARY MEMORY
(128 BYTES)
00h
7Fh127 7F
127 7F
128 80
183 B7
199 C7
200 C8
255 FF
2-WIRE ADDRRESS A0h
DEC HEX
00
MAIN DEVICE
LOWER MEMORY
TABLE SELECT BYTE
PASSWORD ENTRY
(PWE) (4 BYTES)
00h
7Fh
2-WIRE ADDRESS A2h (DEFAULT)
NOTE 1: ADEN BIT = 0. AUXILIARY MEMORY IS ADDRESSED USING THE AUXILIARY DEVICE
NOTE 1. 2-WIRE SLAVE ADDRESS OF A0h, AND THE REMAINDER OF THE MEMORY IS
NOTE 1. ADDRESSED USING THE MAIN DEVICE 2-WIRE SLAVE ADDRESS OF A2h
NOTE 1. (WHEN ADFIX = 0).
NOTE 2: TABLES 00h, 01h, AND 02h DO NOT EXIST.
DEC
MAIN DEVICE
AUXILIARY DEVICE
HEX
00
TABLE 03h
CONFIGURATION
TABLE
80h
B7h
TABLE 04h
RESISTOR 0
LOOK-UP TABLE
(72 BYTES)
80h
C7h
TABLE 05h
RESISTOR 1
LOOK-UP TABLE
(72 BYTES)
80h
C7h
RESERVED AND
CALIBRATION
CONSTANTS
RESERVED AND
CALIBRATION
CONSTANTS
F0h
FFh
F0h
FFh
Figure 2. Memory Organization, ADEN = 0