HCTL-1100 Datasheet, PDF (27/40 Pages) Agilent(Hewlett-Packard) – General Purpose Motion Control ICs

stepper motor. A similar pro-
cedure could be used to combine
the commutator outputs PHA-
PHD with a linear amplifier
interface output (Figure 16) to
create a linear amplifier system.
The Commutator is programmed
by the data in the following
registers. Figure 10 shows an
example of the relationship
between all the parameters.
Status Register (R07H)
Bit #1- 0 = 3-phase configura-
tion, PHA, PHB, and
PHC are active
outputs.
1 = 4-phase configura-
tion, PHA – PHD
are active outputs.
Bit #2- 0 = Rotor position
measured in quad-
rature counts
(4x decoding).
1 = Rotor position
measured in full
counts (1 count = 1
codewheel bar and
space.)
Bit #2 only affects the commuta-
tor’s counting method. This
includes the Ring register
(R18H), the X and Y registers
(R1AH & R1BH), the Offset
register (R1CH), the Velocity
Timer register (R19H), and the
Maximum Advance register
(R1FH).
Quadrature counts (4x decoding)
are always used by the HCTL-
1100 as a basis for position,
velocity, and acceleration control.
Ring Register (R18H)
The Ring register is defined as 1
electrical cycle of the commutator
which corresponds to 1 torque
cycle of the motor. The Ring
register is scalar and determines
the length of the commutation
cycle measured in full or quadra-
ture counts as set by bit #2 in the
Status register (R07H). The value
of the ring must be limited to the
range of 0 to 7FH.
X Register (R1AH)
This register contains scalar data
which sets the interval during
which only one phase is active.
Y Register (R1BH)
This register contains scalar data
which set the interval during
which two sequential phases are
both active. Y is phase overlap. X
and Y must be specified such that:
X + Y = Ring/(# of phases) [5]
These three parameters define the
basic electrical commutation
cycle.
Offset Register (R1CH)
The Offset register contains
two’s-complement data which
determines the relative start of
the commutation cycle with
respect to the index pulse. Since
the index pulse must be physically
referenced to the rotor, offset
performs fine alignment between
the electrical and mechanical
torque cycles.
The Hold Commutator flag (F4)
in the Status register (R07H) is
used to decouple the internal
commutator counters from the
encoder input. Flag (F4) can be
used in conjunction with the
Offset register to allow the user to
advance the commutator phases
open loop. This technique may be
used to create a custom commuta-
tor alignment procedure. For
example, in Figure 10, case 1, for
a three-phase motor where the
ring = 9, X = 3, and Y = 0, the
phases can be made to advance
open loop by setting the Hold
Commutator flag (F4) in the Flag
register (R07H). When the values
0, 1, or 2 are written to the Offset
register, phase A will be enabled.
When the values 3, 4 or 5 are
written to the Offset register,
phase B will be enabled. And,
when the values 6, 7, or 8 are
written to the Offset register,
phase C will be enabled. No
values larger than the value
programmed into the Ring
register should be programmed
into the Offset register.
Phase Advance Registers (R19H,
R1FH)
The Velocity Timer register and
Maximum Advance register
linearly increment the phase
advance according to the
measured speed for rotation up to
a set maximum.
The Velocity Timer register
(R19H) contains scalar data
which determines the amount of
phase advance at a given velocity.
The phase advance is interpreted
in the units set for the Ring
counter by bit #2 in R07H. The
velocity is measured in revolu-
tions per second.
Advance = N_fv∆t
[6]
16 (R19H + 1)
where: ∆t = –––––––––––– [7]
f external clk
N_f = full encoder counts/
revolution.
v = velocity (revolutions/
second)
The Maximum Advance register
(R1FH) contains scalar data
which sets the upper limit for
phase advance regardless of rotor
speed.
Figure 11 shows the relationship
between the Phase Advance
registers. Note: If the phase
advance feature is not used, set
both R19H and R1FH to 0.
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