MPC563XM Reference Manual, Rev. 1
676
Freescale Semiconductor
Preliminary—Subject to Change Without Notice
the next cycle boundary and therefore will be used on cycle
n+1
. The cycle boundary between cycle
n
and
cycle
n+1
is defined as when the internal counter transitions from A1 value in cycle
n
to $1 in cycle
n+1
.
Note that the FLAG is generated at the cycle boundary and has a synchronous operation, meaning that it
is asserted one system clock cycle after the FLAG set event.
Figure 22-46. Modulus Counter Buffered (MCB) Up Count mode
describes the MCB in up/down counter mode (MODE[0:6]=10101bb). A1 register is
updated at the cycle boundary. If A2 is written in cycle
n
, this new value will be used in cycle
n+1
for A1
match. Flags are generated only at A1 match start if MODE[5] is 0. If MODE[5] is set to 1 flags are also
generated at the cycle boundary.
Figure 22-47. Modulus Counter Buffered (MCB) Up/Down Mode
describes in more detail the A1 register update process in up counter mode. The A1 load
signal is generated at the last system clock period of a counter cycle. Thus, A1 is updated with A2 value
at the same time that the counter (EMIOSCNT[n]) is loaded with $1. The load signal pulse has the duration
of one system clock period. If A2 is written within cycle
n
its value is available at A1 at the first clock of
EMIOSCNT[n]
TIME
write to A2
match A1
match A1
match A1
write to A2
$000001
$000005
$000006
$000007
FLAG set event
A1 value
$000006
$000005
$000007
$000007
$000005
$000007
A2 value
FLAG pin/register
Prescaler ratio = 1
cycle n
cycle n+1
cycle n+2
FLAG clear
EMIOSCNT[n]
TIME
write to A2
match A1
match A1
write to A2
$000001
$000005
$000006
$000007
FLAG set event
A1 value
$000006
$000005
$000007
$000005
$000007
A2 value
FLAG pin/register
Prescaler ratio = 1
cycle n+1
cycle n+2
cycle n
FLAG clear