MPC563XM Reference Manual, Rev. 1
Freescale Semiconductor
677
Preliminary—Subject to Change Without Notice
cycle
n+1
and the new value is used for match at cycle
n+1
. The update disable bits OU[n] of
EMIOSOUDIS register can be used to control the update of this register, thus allowing to delay the A1
register update for synchronization purposes.
Figure 22-48. MCB Mode A1 Register Update in Up Counter Mode
describes the A1 register update in up/down counter mode. Note that A2 can be written at
any time within cycle
n
in order to be used in cycle
n+1
. Thus A1 receives this new value at the next cycle
boundary. Note that the update disable bits OU[n] of EMIOSOUDIS register can be used to disable the
update of A1 register.
Figure 22-49. MCB Mode A1 Register Update in Up/Down Counter Mode
22.5.1.1.13
Output Pulse Width and Frequency Modulation (OPWFM) Mode
In this mode, duty cycle of output signal is the value defined in register A1 plus one and the period is the
value defined in register B1 plus one. MODE[6] bit controls the transfer from register B2 to B1, which can
be done either immediately (MODE[6] cleared, MODE[0:6]=00110b0), providing the fastest change in the
duty cycle, or at every match of register A1 (MODE[6] set, MODE[0:6]=00110b1).
A1 value $000008
$000008
$000001
internal counter
$000004
$000006
A2 value $000008
$000004
$000006
$000002
$000004
$000006
write to A2
write to A2
Match A1
Match A1
A1 load signal
8
4
6
Match A1
Counter = A1
Time
cycle n
cycle n+1
cycle n+2
Prescaler ratio = 2
A1 value
$000006
A2 value $000006
$000005
$000006
$000005
A1 load signal
Counter = 2
EMIOSCNT[n]
TIME
write to A2
match A1
match A1
write to A2
$000001
$000005
$000006
$000006
cycle n
cycle n+1
cycle n+2
Prescaler ratio = 2