AD5255BRU25-RL7 データシートの表示（PDF） - Analog Devices
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AD5255BRU25-RL7 Datasheet PDF : 20 Pages
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Table 6. RDAC R/W EEPROM Addresses (CMD/REG = 0, EE/RDAC = 1)
A4
A3
A2
A1
A0
Byte Description
0
0
0
0
0
RDAC0 8 LSBs
0
0
0
0
1
RDAC0 MSB
0
0
0
1
0
RDAC1 8 LSBs
0
0
0
1
1
RDAC1 MSB
0
0
1
0
0
RDAC2 7 bits
0
0
1
0
1
11 bytes RDAC User EEPROM
. . . to . . .
0
1
1
1
1
AD5255
Table 7. RDAC Command Table (CMD/REG = 1)
C3
C2
C1
C0
Command Description
0
0
0
0
0
0
0
1
0
0
1
0
NOP
Restore EEPROM to RDAC1
Store RDAC to EEPROM2
0
0
1
1
Decrement RDAC 6 dB
0
1
0
0
Decrement All RDACs 6 dB
0
1
0
1
Decrement RDAC 1 Step
0
1
1
0
0
1
1
1
Decrement All RDACs 1 Step
Reset; Restore EEPROM to all RDACs2
1
0
0
0
Increment RDACs 6 dB
1
0
0
1
Increment All RDACs 6 dB
1
0
1
0
Increment RDAC 1 Step
1
0
1
1
Increment All RDAC 1 Step
1
1
0
0
Reserved
. . . to . . .
1
1
1
1
1 Command leaves the device in the EEPROM read power state. Issue the NOP command to return the device to the idle state.
2 Command requires acknowledge polling after execution.
RDAC Interface Operation
Each programmable resistor wiper setting is controlled by
specific RDAC registers, as shown in Table 5. Each RDAC
register corresponds to an EEPROM memory location,
which provides nonvolatile wiper storage functionality.
RDAC registers and their corresponding EEPROM memory
locations are programmed and read independently from each
other. The RDAC register is refreshed by the EEPROM locations
either with a hardware reset via Pin 1, or by issuing one of the
various RDAC register load commands shown in the Table 7.
RDAC Write
Setting the wiper position requires an RDAC write operation,
shown in Figure 22. RDAC write operations follow a format
similar to the EEPROM write interface. The only difference
between an RDAC write and an EEPROM write operation
is the use of an RDAC address byte in place of the memory
address used in the EEPROM write operation. The RDAC
address byte is described in detail in Table 5 and Table 6.
As with the EEPROM write operation, any RDAC EEPROM
(Shortcut Command 2) write operation disables the I2C inter-
face during the internal write cycle. Acknowledge polling, as
described in the EEPROM Interface section, is required to
determine whether the write cycle is complete.
RDAC Read
The AD5255 provides two RDAC read operations. The first,
shown in Figure 23, reads the contents of the current RDAC
address counter. Figure 24 illustrates the second read operation,
which allows users to specify which RDAC register to read by
first issuing a dummy write command to change the RDAC
address pointer, and then proceeding with the RDAC read
operation at the new address location.
The read-only RDAC EEPROM memory locations can also be
read by using the address and bits specified in Table 6.
Rev. A | Page 13 of 20
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