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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)

7 BITS FOR INTEGER NUMBER

SIGN

SIGN

A

A

D6

D5

D4

D3

D2

D1

D0

D7

A

D6

D5

D4

D3

D2

D1

D0

D7

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.