ST7FMC1K2B3 STMICROELECTRONICS [STMicroelectronics], ST7FMC1K2B3 Datasheet - Page 174

• Manufacturer Part Number: ST7FMC1K2B3
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ST7MC1xx/ST7MC2xx
MOTOR CONTROLLER (Cont’d)
Note on using the auto-updated MTIM timer:
The auto-updated MTIM timer works accurately
within its operating range but some care has to be
taken when processing timer-dependent data such
as the step duration for regulation or demagnetiza-
tion.
For example if an overflow occurs when calculat-
ing
(MCOMP+demagnetisation_time>FFh), the value
that is stored in MDREG will be:
80h+(MCOMP+demagnetization_time-FFh)/2.
Note on commutation interrupts: It is good prac-
tice to modify the configuration for the next step as
soon as possible, i.e within the commutation inter-
rupt routine.
All registers that need to be changed at each step
have a preload register that enables the modifica-
tions for a complete new configuration to be per-
formed at the same time (at C event in normal
mode or when writing the MPHST register in direct
access mode).
174/309
1
a
simulated
end
of
demagnetization
These configuration bits are:
CPB, HDM, SDM and OS2 in the MCRB register
and IS[1:0], OO[5:0] in the MPHST register.
Note on initializing the MTC: As shown in
all the MTIM timer registers are in read-write mode
until the MTC clock is enabled (with the CKE bit).
This allows the timer, prescaler and compare reg-
isters to be properly initialized for start-up.
In sensorless mode, the motor has to be started in
switched mode until a BEMF voltage is present on
the inputs. This means the prescaler ST[3:0] bits
and MCOMP register have to be modified by soft-
ware. When running the ST[3:0] bits can only be
incremented / decremented, so the initial value is
very important.
When starting directly in autoswitched mode (in
sensor mode for example), write an appropriate
value in the MZREG and MZPRV register to per-
form a step calculation as soon as the clock is en-
abled.
Table 41