MPC563XM Reference Manual, Rev. 1
688
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
Figure 22-59. OPWMCB A1 and B1 registers load
The OU[n] bit of EMIOSOUDIS register can be used to disable the A1 and B1 updates, thus allowing to
synchronize the load on these registers with the load of A1 or B1 registers in others channels. Note that
using the update disable bit A1 and B1 registers can be updated at the same counter cycle thus allowing to
change both registers at the same time.
In this mode A1 matches always sets the internal counter to $1. When operating with leading edge dead
time insertion the first A1 match sets the internal counter to $1. When a match occurs between register B1
and the internal time base, the output flip-flop is set to the value of the EDPOL bit. In the following match
between register A1 and the selected time base, the output flip-flop is set to the complement of the EDPOL
bit. This sequence repeats continuously. The internal counter should not reach $0 as consequence of a
rollover. In order to avoid it the user should not write to EMIOSB register a value greater than twice the
difference between external count up limit and EMIOSA value.
shows two cycles of a Center Aligned PWM signal. Note that both A1 and B1 register values
are changing within the same cycle which allows to vary at the same time the duty cycle and dead time
values.
A1 value
$000020
A2 value $000020
$000015
$000016
$000015
A1/B1 load signal
Selected Counter == 2
Selected
TIME
write to A2
write to B2
write to B2
write to A2
$000001
$000005
$000006
$000016
cycle n
cycle n+1
cycle n+2
Counter Bus
B1 value
$000004
B2 value $000004
$000005
$000006
$000005
$000006
Prescaler ratio = 2
System Clock