HCTL1100 Datasheet, PDF (22/40 Pages) Agilent(Hewlett-Packard) – General Purpose Motion Control ICs

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When any Control mode is being
executed, the unadjusted internal
2’s-complement motor command
is written to R09H. Because of the
hardware limit on the linear range
(64H to 9CH, ± 100D), the PWM
port saturates sooner than the 8-
bit Motor Command port (00H to
FFH, +127D to –128D). When
the internal motor command
saturates above 8 bits, the PWM
port is saturated to the full
± 100% duty cycle level. Figure 5
shows the actual values inside the
PWM port. Note that the Unipolar
flag, F2, does not affect the PWM
port.
For commutation of brushless
motors with the PWM port, only
use the Pulse pin from the PWM
port as the commutator already
contains sign information. (See
Figure 9.)
The PWM port has an option that
can be used with H-bridge type
amplifiers. The option is Sign
Reversal Inhibit, which inhibits
the Pulse output for one PWM
period after a sign polarity
reversal. This allows one pair of
transistors to turn off before
others are turned on and thereby
avoids a short across the power
supply. Bit 0 in the Status register
(R07H) controls the Sign Reversal
Figure 5. PWM Port Output.
Figure 6. Sign Reversal Inhibit.