s3c72m9 Samsung Semiconductor, Inc., s3c72m9 Datasheet - Page 254

• Manufacturer Part Number: s3c72m9
• Description: The S3c72m5/s3c72m7/s3c72m9 Single-chip Cmos Microcontroller Has Been Designed For High Performance Using Samsung S
• Manufacturer: Samsung Semiconductor, Inc.

TIMERS and TIMER/COUNTERS
BASIC TIMER COUNTER (BCNT)
BCNT is an 8-bit counter for the basic timer. It can be addressed by 8-bit read instructions.
counter value undetermined. BCNT is automatically cleared to logic zero whenever the BMOD register control bit
(BMOD.3) is set to "1" to restart the basic timer. It is incremented each time a clock pulse of the frequency
determined by the current BMOD bit settings is detected.
When BCNT has incrementing to hexadecimal ‘FFH’ ( 255 clock pulses), it is cleared to ‘00H’ and an overflow is
generated. The overflow causes the interrupt request flag, IRQB, to be set to logic one. When the interrupt request is
generated, BCNT immediately resumes counting incoming clock signals.
BASIC TIMER OPERATION SEQUENCE
The basic timer's sequence of operations may be summarized as follows:
1. Set BMOD.3 to logic one to restart the basic timer
2. BCNT is then incremented by one after each clock pulse corresponding to BMOD selection
3. BCNT overflows if BCNT = 255 (BCNT = FFH)
4. When an overflow occurs, the IRQB flag is set by hardware to logic one
5. The interrupt request is generated
6. BCNT is then cleared by hardware to logic zero
7. Basic timer resumes counting clock pulses
11-6
Always execute a BCNT read operation twice to eliminate the possibility of reading unstable data while the
counter is incrementing. If, after two consecutive reads, the BCNT values match, you can select the latter
value as valid data. Until the results of the consecutive reads match, however, the read operation must be
repeated until the validation condition is met.
NOTE
S3C72M5/C72M7/C72M9/P72M9 (Preliminary Spec)
RESET
leaves the BCNT