HCTL-1101 Datasheet, PDF (32/40 Pages) AVAGO TECHNOLOGIES LIMITED – General Purpose Control ICs Position and Velocity Control Low Power CMOS

The command and actual velocity are 16-bit two’s-com-
plement words.
The command velocity resides in registers R24H (MSB) and
R23H (LSB). These registers are unlatched which means
that the command velocity will change to a new velocity
as soon as the value in either R23H or R24H is changed.
The registers can be read or written to in any order.
The units of velocity are quadrature counts/sample time.
To convert from rpm to quadrature counts/sample time,
use the formula shown below:
Where:
Vq = velocity in quadrature counts/sample time
Vr = velocity in rpm
N = 4 times the number of slots in the codewheel
(i.e., quadrature counts).
t = The HCTL-1101 sample time in seconds.
(See the section on the HCTL-1101’s Sample Timer regis-
ter).
Because the Command Velocity registers (R24H and R23H)
are internally interpreted by the HCTL-1101 as 12 bits of
integer and 4 bits of fraction, the host processor must
multiply the desired command velocity (in quadrature
counts/sample time) by 16 before programming it into
the HCTL-1101’s Command Velocity registers.
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