Rainbow Electronics DS1876 - Manual (Page 23)

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DS1876
SFP Controller with Dual LDD Interface
Auxiliary Memory (Device A0h) contains 256 bytes
of EE memory accessible from address 00h–FFh. It is
selected with the device address of A0h.
See the Register Descriptions section for a more com-
plete detail of each byte’s function, as well as for read/
write permissions for each byte.
Shadowed EEPROM
Many nonvolatile memory locations (listed within the
Register Descriptions section) are actually shadowed
EEPROM and are controlled by the SEEB bit in Table
02h, Register 80h.
The DS1876 incorporates shadowed EEPROM memory
locations for key memory addresses that can be writ-
ten many times. By default the shadowed EEPROM bit,
SEEB, is not set and these locations act as ordinary
EEPROM. By setting SEEB, these locations function
like SRAM cells, which allow an infinite number of write
cycles without concern of wearing out the EEPROM.
This also eliminates the requirement for the EEPROM
write time, t
WR . Because changes made with SEEB
enabled do not affect the EEPROM, these changes are
not retained through power cycles. The power-on value
is the last value written with SEEB disabled. This func-
tion can be used to limit the number of EEPROM writes
during calibration or to change the monitor thresholds
periodically during normal operation helping to reduce
the number of times EEPROM is written. Figure 14 shows
the memory map and indicates which locations are
shadowed EEPROM.
Figure 14. Memory Map
EEPROM
(256 BYTES)
FFh
I 2 C ADDRESS A0h I 2 C ADDRESS A2h/B2h
AUXILIARY DEVICE
MAIN DEVICES AT A2h AND B2h
00h
ALARM-
ENABLE ROW
(8 BYTES)
PASSWORD ENTRY
(PWE) (4 BYTES)
TABLE-SELECT
BYTE
FFh
80h
F8h
MOD1/2
OFFSET LUT
FFh
F8h
TABLE 01h
(A2h ONLY)
EEPROM
(120 BYTES)
F7h
7Fh
00h
LOWER
MEMORY
FFh
80h
TABLE 02h
NONLOOKUP
TABLE CONTROL
AND
CONFIGURATION
REGISTERS
(B2h ONLY CONTAINS
TRANSMITTER 2-
RELATED REGISTERS)
80h
TABLE 04h
MOD1 (A2h)
MOD2 (B2h)
LOOKUP TABLE
(72 BYTES)
C7h
F8h TABLE 05h
ALARM-ENABLE ROW
(8 BYTES)
ALARM-ENABLE ROW
CAN BE CONFIGURED
TO EXIST AT TABLE 01h
OR TABLE 05h USING
MASK BIT IN TABLE 02h,
REGISTER 88h.
FFh
NOTE 1: IF ASEL = 0, THEN THE MAIN DEVICE I 2 C SLAVE ADDRESS IS A2h/B2h.
IF ASEL = 1, THEN THE MAIN DEVICE I 2 C SLAVE ADDRESS IS DETERMINED BY THE VALUE IN
TABLE 02h, REGISTER 8Bh.
NOTE 2: TABLE 00h DOES NOT EXIST.
NOTE 3: ALARM-ENABLE ROW CAN BE CONFIGURED TO EXIST AT TABLE 01h OR TABLE 05h USING THE
MASK BIT IN TABLE 02h, REGISTER 88h.
(APC1/2, HBATH1/2,
TXP HI 1/2, TXP LO 1/2)
OFFSET LUT
FFh
E0h
80h
TABLE 06h
APC1 (A2h)
APC2 (B2h)
LOOKUP TABLE
(72 BYTES)
C7h