Motorola DSP96002 6 INTRODUCTION TO THE TIMER/EVENT COUNTER

28 MOTOROLA
6 INTRODUCTION TO THE TIMER/EVENT COUNTER
This section describes the two identical and independent timer/event counter modules
now featured on the DSP96002. The timer can use inter nal or external clocking and can
interrupt the processor after a number of e vents specified b y a user program, or it can sig-
nal an e xternal de vice after counting internal e v ents. The timer can also be used to trigger
DMA transfers after a specified number of events (clocks) occurs.
Each timer connects to the e xternal world through its own bidirectional TIO pin. When TIO
is used as input, the module is functioning as an exter nal event counter or is measuring
e xternal pulse width/signal period. When TIO is used as output, the module is functioning
as a timer and TIO becomes the timer pulse. When the TIO pin is not used by the timer
module it can be used as a general purpose I/O (GPIO) pin.
Note: When the timer is disabled, the TIO pin becomes three-stated. To prevent undes-
ired spikes from occurring, the TIO pin should be pulled up or down when it is not in use.
6.1 TIMER BLOCK DIAGRAM
Figure 5 shows a block diagram of the timer module. It includes a 32-bit read-write Timer
Control and Status Register (TCSR), a 32-bit read-write Timer Count Register (TCR), a
32-bit counter, and logic for clock selection and interrupt generation.
Figure 5 - Single Timer Module Block Diagram
Register addresses are shown in Figure 5 on page 28.
GDB
Timer Control/Status Register (TCSR)
Interrupt
C
o
u
n
t
e
r
T
C
R
INV bit TE bit
TC2-TC0
TIO
CLK/2
0
1
DIR
3
24
24
24
111
32
TIE bit