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Maxim > Design Support > Technical Documents > Application Notes > Digital Potentiometers > APP 3481
Maxim > Design Support > Technical Documents > Application Notes > Optoelectronics > APP 3481
Keywords: DS1859, SFF-8472, MSA, Fiber Optics, app note 3481
APPLICATION NOTE 3481
Using the DS1859 with External EEPROM
Mar 23, 2005
Abstract: This application note addresses adding external EEPROM into SFF-8472 applications that
require more than 128 Bytes of memory located at the I²C* device address A0h.
Introduction
The DS1859 is a dual digital resistor that automatically adjusts itself as a function of temperature to the
values programmed into a EEPROM look-up table (LUT). Other features include five analog-to-digital
channels (including V
CC
and temperature) and a memory map that is compatible with SFF-8472 fiber
optic applications. This application note addresses adding external EEPROM into SFF-8472 applications
that require more than 128 Bytes of memory at I²C device address A0h.
DS1859 Default Memory Configuration
By default, the DS1859 responds to two I²C addresses (Figure 1). It provides 128 Bytes of general-
purpose EEPROM memory at I²C address A0h, which is called the auxiliary memory. The main device
address (A2h) is used to configure and access the rest of the chips resources. The main memory is
partitioned into a lower memory section (the first 128 Bytes) that is always accessible, and an upper
memory section that is used to access several tables of memory that begin at address 80h. These tables
of memory are selected by the table-select Byte (address 7F, in lower memory).
Figure 1. DS1859 default memory map.
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