AD527x resistor performance mode

Hi,

I plan to use AD527x for a project where the absolute resistor tolerance is a key parameter.

I got confused on the device DS. For the resistor performance mode DS tells "...code = half scale, RWA = 10 kΩ ± 100 Ω. See Table 2, Table 3, Table 5, and Table 6 to verify which codes achieve ±1% resistor tolerance."  

  • What does code=half mean?

Table 2 says that the 1% code range is for 2.7<Vdd<5.5V "From 0x0BE to 0x3FF" This is not the half range.

DS later says, "Rheostat Operation—1% Resistor Tolerance The nominal resistance between Terminal W and Terminal A, RWA, is 20 kΩ, 50 kΩ, or 100 kΩ and has 1024-/256-tap points accessed by the wiper terminal. " The formula uses RWA to calculate the actual value. 

  • What is the RWA value in 1% accuracy mode I should calculate with if purchasing a 20k device, 10k or 20k? 10k is specified in performance mode details above and 20k is specified in rheostat operation 1% tolerance.

Thanks,

T