FUJITSU MB91460 SERIES FR60 - Manual (Page 899)

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Chapter 43 Stepper Motor Controller
4.Caution
4. Caution
The caution when using the stepping motor controller are described below.
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Caution when Changing PWM Setting
The PWM compare registers 1&2 (PWC1, PWC2) and the PWM selection registers 1&2 (PWS1, PWS2) can be
accessed at any time. However, to change setting of the "H" width of PWM or to change the PWM output, "1"
must be written to the BS bit of the PWM2 selection register after (or and at the same time) a setting is written to
those registers (the PWM compare register 1&2 and the PWM selection register 1&2).
When "1" is set to the BS bit, the new setting is enabled at the end of the current PWM cycle and the BS bit is
cleared automatically.
Also, when "1" is written to the BS bit and the BS bit is reset at the end of the PWM cycle simultaneously, "1" is
written to the BS and resetting of the BS bit is cancelled.