Question
We are using AD2S1210 IC for our project. I have the following query, after reading the data sheet for the AD2S1210 IC. Please read page (28/36) inthe datasheet.
1. In case of configuration mode (during read for AD2S1210, only 8-bit are shifted out through SDO pins. In that D7 bit will contain fault data andD6-D0 contains the data which is to be read), so when I need to read position register\velocity register value, how can I read all 16 bits of data?
2. As per my understanding, to read all 16 bits I need to send lower position register address (0x80) first to read lower 8-bits and then the higherbyte address (0x81) to read high byte (8-bits). But the problem here is, in the 8-bits which is shifted out to SDO D7 bit will contain fault data,only D6-D0 will have position register value which means in case if I try to read the position register value by sending lower byte address first andthen higher byte address I can read only 14 bits of position data and 2 bits of fault data (which comes from 2 D7 bits)
cycle 1st 2ndaddress 0x80 0x81data D7-fault, D6-D0 - position D7-fault, D6-D0 - position => only 14 bits is of position data, 2 bits of fault data
Due to D7 bit (fault data), I think I will miss two bits of position data. So how can I read all the 16 bits of data?
Please help me in resolving this query as early as possible.
Answer
1. Yes it is possible to read all 16-bit velocity and angular position data in configuration mode. A typical sequence for position would be asfollows (velocity is based on the same principle just different register addresses)
cycle -> 1st 2ndaddress -> 0x80 0x81data -> D15-D8 – position D7-D0 – positionThe velocity and position registers are “Read Only” registers and therefore are not user programmable. They do not therefore containa fault bit, just 8 data bits.
2. For 16-bit resolution as you suggest 1 LSB represents 0.32958984375 arc minutes or 0.0054931640625 degrees.For velocity at the various resolutions with a 8.192MHz clock 1 LSB represents the following, (the MSB represents direction)10-bit 2500rps/2^9 = 4.8828125rps12-bit 1000rps/2^11 = 0.48828125rps14-bit 500rps/2^13 = 0.030517578rps ( there appears to be a typo with regards to this spec in the datasheet)16-bit 125rps/2^15 = 0.003814697rps
Please be aware that velocity is a function of the clock frequency so if you scale the clock you must also scale the velocity results linearly.
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