Rainbow Electronics DS2770 - Manual (Page 15)

DS2770
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EEPROM REGISTER
Figure 13 shows the format of the EEPROM Register. The function of each bit is described in detail in
the following paragraphs.
EEPROM REGISTER FORMAT Figure 13
Address 07
bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0
EEC LOCK X X X BL2 BL1 BL0
EEC — EEPROM Copy Flag. A 1 in this read-only bit indicates that a Copy Data command is in
progress. While this bit is high, writes to EEPROM addresses are ignored. A 0 in this bit indicates that
data may be written to unlocked EEPROM blocks.
LOCK — EEPROM Lock Enable. This bit is used to enable the Lock command by writing a 1 to it prior
to issuing the command. When this bit is 0, the Lock command is ignored. After the Lock command is
executed, the Lock bit is reset to 0. The Lock bit will also be reset by any other command issued after the
bit has been set. The factory default is 0.
BL2 — EEPROM Block 2 Lock Flag. A 1 in this read-only bit indicates that EEPROM Block 2
(addresses 40 to 47h) is locked (read-only) while a 0 indicates Block 2 is unlocked (read/write).
BL1 — EEPROM Block 1 Lock Flag. A 1 in this read-only bit indicates that EEPROM Block 1
(addresses 30 to 3Fh) is locked (read-only) while a 0 indicates Block 1 is unlocked (read/write).
BL0 — EEPROM Block 0 Lock Flag. A 1 in this read-only bit indicates that EEPROM Block 0
(addresses 20 to 2Fh) is locked (read-only) while a 0 indicates Block 0 is unlocked (read/write).
X — Reserved Bits.
1-WIRE BUS SYSTEM
The 1-Wire bus is a system that has a single bus master and one or more slaves. A multidrop bus is a
1-Wire bus with multiple slaves. A single-drop bus has only one slave device. In all instances, the
DS2770 is a slave device. The bus master is typically a microprocessor in the host system. The discussion
of this bus system consists of four topics: 64-bit Net Address, Hardware Configuration, Transaction
Sequence, and 1-Wire Signaling.
64-BIT NET ADDRESS
Each DS2770 has a unique factory-programmed 1-Wire net address that is 64 bits in length. The first
eight bits are the 1-Wire family code (2Eh for DS2770). The next 48 bits are a unique serial number. The
last eight bits are a CRC of the first 56 bits (see Figure 14). The 64-bit net address and the 1-Wire I/O
circuitry built into the device enable the DS2770 to communicate through the 1-Wire protocol detailed in
the 1-Wire Bus System section of this data sheet.