Datasheet

C515C
Data Sheet 38 2003-02
Compare Mode 1
If compare mode 1 is enabled and the software writes to the appropriate output latch at
the port, the new value will not appear at the output pin until the next compare match
occurs. Thus, it can be choosen whether the output signal has to make a new transition
(1-to-0 or 0-to-1, depending on the actual pin-level) or should keep its old value at the
time when the timer value matches the stored compare value.
In compare mode 1 (see Figure 14) the port circuit consists of two separate latches. One
latch (which acts as a “shadow latch”) can be written under software control, but its value
will only be transferred to the port latch (and thus to the port pin) when a compare match
occurs.
Figure 14 Compare Function in Compare Mode 1
MCS02662
Latch
Port
Q
QCLK
D
Read Pin
DD
V
D
CLK
Q
Shadow
Latch
Read Latch
Port Circuit
Internal
Bus
Latch
Write to
Compare Reg.
Compare Register
Circuit
Comparator
Timer Register
Timer Circuit
Compare
Match
Pin
Port
16 Bit
16 Bit