
S3C7559/P7559
TIMERS and TIMER/COUNTERS
11-5
BASIC TIMER MODE REGISTER (BMOD)
The basic timer mode register, BMOD, is a 4-bit write-only register. Bit 3, the basic timer start control bit, is also
1-bit addressable. All BMOD values are set to logic zero following
RESET and interrupt request signal
generation is set to the longest interval. (BT counter operation cannot be stopped.) BMOD settings have the
following effects:
— Restart the basic timer;
— Control the frequency of clock signal input to the basic timer;
— Determine time interval required for clock oscillation to stabilize following the release of stop mode by an
interrupt.
By loading different values into the BMOD register, you can dynamically modify the basic timer clock frequency
during program execution. Four BT frequencies, ranging from fxx/212 to fxx/25, are selectable. Since BMOD's
reset value is logic zero, the default clock frequency setting is fxx/212.
The most significant bit of the BMOD register, BMOD.3, is used to restart the basic timer. When BMOD.3 is set
to logic one by a 1-bit write instruction, the contents of the BT counter register (BCNT) and the BT interrupt
request flag (IRQB) are both cleared to logic zero, and timer operation is restarted.
The combination of bit settings in the remaining three registers — BMOD.2, BMOD.1, and BMOD.0 — determine
the clock input frequency and oscillation stabilization interval.
Table 11-2. Basic Timer Mode Register (BMOD) Organization
BMOD.3
Basic Timer Start Control Bit
1
Start basic timer; clear IRQB, BCNT, and BMOD.3 to "0"
BMOD.2
BMOD.1
BMOD.0
Basic Timer Input
Clock
Interrupt Interval Time
(wait time when stop mode is released)
0
fxx/212 (0.87 kHz)
220/fxx (292.9 ms)
0
1
fxx/29 (6.99 kHz)
217/fxx (36.6 ms)
1
0
1
fxx/27 (27.9 kHz)
215/fxx (9.15 ms)
1
fxx/25 (111.8 kHz)
213/fxx (2.29 ms)
NOTES:
1.
Clock frequencies and interrupt interval time assume a system oscillator clock frequency (fxx) of 3.579545 MHz.
2.
fxx = system clock frequency.
3.
Wait time is the time required to stabilize clock signal oscillation after stop mode is released.
4.
The standard stabilization time for system clock oscillation following a
RESET is 36.6 ms at 3.579545 MHz.