AD5255(Rev0) 查看數據表（PDF） - Analog Devices
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AD5255 Datasheet PDF : 20 Pages
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AD5255
RDAC Shortcut Commands
Eleven “shortcut” commands are provided for easy manipulation
of RDAC registers and their corresponding EEPROM memory
locations. These commands are shown in Table 9. A more detailed
discussion about the RDAC shortcut commands can be found
in the Theory of Operation section.
The interface for issuing an RDAC shortcut command is shown
in Figure 25. All shortcut commands require acknowledge
polling to determine whether the command has finished
executing.
RDAC Resistor Tolerance
The end-to-end resistance tolerance for each RDAC channel is
stored in read-only memory during factory production. This
information is read by using the address and bits specified in
Table 8.
Tolerance values are stored in percentage form. Figure 26 shows
the format of the tolerance data stored in memory. Each stored
tolerance uses two memory locations. The first location stores
the integer portion, while the second location stores the decimal
portion.
The resistance tolerance is stored in sign-magnitude format.
The MSB of the first memory location designates the sign
(0 = +, 1 = −) and the remaining 7 LSBs are designated for the
integer portion of the tolerance. All 8 bits of the second
memory location are represented the decimal portion of the
tolerance value.
Table 8. Addresses for Reading Tolerance (CMD/REG = 0, EE/RDAC = 1, A4 = 1)
A4 A3 A2 A1 A0 Data Byte Description
1
1
0
0
0
Sign and 7-Bit Integer Values of RDAC0 Tolerance (Read-Only)
1
1
0
0
1
8-Bit Decimal Value of RDAC0 Tolerance (Read-Only)
1
1
0
1
0
Sign and 7-Bit Integer Values of RDAC1 Tolerance (Read-Only)
1
1
0
1
1
8-Bit Decimal Value of RDAC1 Tolerance (Read-Only)
1
1
1
0
0
Sign and 7-Bit Integer Values of RDAC2 Tolerance (Read-Only)
1
1
1
0
1
8-Bit Decimal Value of RDAC2 Tolerance (Read-Only)
A
D7
D6
D5
D4
D3
D2
D1
D0
A
D7
D6
D5
D4
D3
D2
D1
D0
A
SIGN
26
25
24
23
22
21
20
2–1
2–2
2–3
2–4
2–5
2–6
2–7
2–8
SIGN
7 BITS FOR INTEGER NUMBER
8 BITS FOR DECIMAL NUMBER
Figure 26. Format of Stored Tolerance in Sign Magnitude with Bit Positions Descriptions Unit is in %. Only Data Bytes Shown.
Rev. 0 | Page 14 of 20
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