ST72321B STMICROELECTRONICS [STMicroelectronics], ST72321B Datasheet - Page 63

• Manufacturer Part Number: ST72321B
• Description: 64/44-pin 8-bit MCU with 32 to 60K Flash/ROM, ADC, five timers, SPI, SCI, I2C interface
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

ON-CHIP PERIPHERALS (Cont’d)
Output compare and Time base interrupt
On overflow, the OVF flag of the ARTCSR register
is set and an overflow interrupt request is generat-
ed if the overflow interrupt enable bit, OIE, in the
ARTCSR register, is set. The OVF flag must be re-
set by the user software. This interrupt can be
used as a time base in the application.
Figure 41. External Event Detector Example (3 counts)
f
EXT
COUNTER
=f
COUNTER
OVF
FDh
FEh
ARTARR=FDh
FFh
INTERRUPT
IF OIE=1
FDh
External clock and event detector mode
Using the f
auto-reload timer can be used as an external clock
event detector. In this mode, the ARTARR register
is used to select the n
be counted before setting the OVF flag.
Caution: The external clock function is not availa-
ble in HALT mode. If HALT mode is used in the ap-
plication, prior to executing the HALT instruction,
the counter must be disabled by clearing the TCE
bit in the ARTCSR register to avoid spurious coun-
ter increments.
ARTCSR READ
FEh
EXT
n
EVENT
FFh
external prescaler input clock, the
INTERRUPT
IF OIE=1
= 256 - ARTARR
EVENT
FDh
ARTCSR READ
number of events to
t
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