參數(shù)資料
型號(hào): AD5253EVAL
廠商: Analog Devices, Inc.
元件分類(lèi): 通用總線功能
英文描述: Dual, 256-Tap, Nonvolatile, I2C-Interface, Digital Potentiometers
中文描述: 雙路、256抽頭、非易失、I2C接口、數(shù)字電位器
文件頁(yè)數(shù): 18/28頁(yè)
文件大?。?/td> 834K
代理商: AD5253EVAL
AD5253/AD5254
Table 10. Address Table 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)
1
1
1
1
0
Sign and 7-Bit Integer Values of RDAC3 Tolerance (Read Only)
1
1
1
1
1
8-Bit Decimal Value of RDAC3 Tolerance (Read Only)
Rev. 0 | Page 18 of 28
0
A
A
A
D7
D6
D5
D4
D3
D2
D1
D0
SIGN
SIGN
7 BITS FOR INTEGER NUMBER
2
6
2
5
2
4
2
3
2
2
2
1
2
0
D7
D6
D5
D4
D3
D2
D1
D0
8 BITS FOR DECIMAL NUMBER
2
–8
2
–1
2
–2
2
–3
2
–4
2
–5
2
–6
2
–7
Figure 32. Format of Stored Tolerance in Sign Magnitude Format with Bit Position Descriptions. Unit is %. Only Data Bytes Are Shown.
R
AB
Tolerance Stored in Read-Only Memory
AD5253/AD5254 feature patented R
AB
tolerances storage in the
nonvolatile memory. The tolerance of each channel is stored in
the memory during the factory production and can be read by
users at any time. The knowledge of the stored tolerance, which
is the average of R
AB
overall codes (Figure 29), allows users to
predict R
AB
accurately. This feature is valuable for precision,
rheostat mode, or open-loop applications where knowledge of
absolute resistance is critical.
The stored tolerances reside in the read-only memory, and are
expressed in percent. The tolerance is coded in sign magnitude
binary, 16 bits long, and is stored in two memory locations (see
Table 10). The data format of the tolerance is the sign magni-
tude binary format; an example is shown in Figure 32. In the
first memory location of the eight data bits, the MSB is
designated for the sign (0 = + and 1= –) and the 7 LSBs are
designated for the integer portion of the tolerance. In the
second memory location, all eight data bits are designated for
the decimal portion of tolerance. As shown in Table 8 and
Figure 32, for example, if the rated R
AB
= 10 k and the data
readback from address 11000 shows 0001 1100 and address
11001 shows 0000 1111, then RDAC0 tolerance can be
calculated as:
MSB: 0 = +
Next 7 MSB: 001 1100 = 28
8 LSB: 0000 1111 = 15 × 2
–8
= 0.06
Tolerance = +28.06% and therefore
R
AB_ACTUAL
= 12.806 k
EEMEM Write-Acknowledge Polling
After each write operation to the EEMEM registers, an internal
write cycle begins. The I
2
C interface of the device is disabled. In
order to determine if the internal write cycle is complete and
the I
2
C interface is enabled, interface polling can be executed.
I
2
C interface polling can be conducted by sending a start condi-
tion followed by the slave address + the write bit. If the I
2
C
interface responds with an ACK, the write cycle is complete and
the interface is ready to proceed with further operations. Other-
wise, I
2
C interface polling can be repeated until it succeeds.
Commands 2 and 7 also require acknowledge polling.
EEMEM Write Protection
Setting the WP pin to a logic LOW after EEMEM programming
protects the memory and RDAC registers from future write
operations. In this mode, the EEMEM and RDAC read
operations operate as normal. When write protection is enabled,
commands 1 (restore from EEMEM to RDAC) and 7 (reset)
function normally to allow RDAC settings to be refreshed from
the EEMEM to the RDAC registers.
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