Legacy-Free Keyboard/Embedded Controller with SPI and LPC Docking Interface
Table 23.6 RTC Divider Selection Bits
OSCILLATOR
FREQUENCY
REGISTER A BITS
MODE
32.768 kHz
DV2
0
DV1
0
DV0
0
Normal Operation
Reset Divider
Normal Operation
Oscillator Disabled
Test
0
0
1
0
1
0
0
1
1
1
0
X
1
1
X
Reset Divider
RS3-0
The four rate selection bits select one of 15 taps on the divider chain or disable the divider output. The
selected tap determines rate or frequency of the periodic interrupt. The program may enable or disable
the interrupt with the PIE bit in Register B. Table 23.7 lists the periodic interrupt rates and equivalent
output frequencies that may be chosen with the RS0-RS3 bits. These four bits are read/write bits which
are not affected by VCC1 POR.
Table 23.7 RTC Periodic Interrupt Rates
RATE SELECT
32.768 KHZ TIME BASE
RS3 RS2 RS1 RS0
PERIOD RATE OF INTERRUPT
FREQUENCY OF INTERRUPT
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0.0
3.90625 ms
7.8125 ms
122.070 µs
244.141 µs
488.281 µs
976.562 µs
1.953125 ms
3.90625 ms
7.8125 ms
15.625 ms
31.25 ms
62.5 ms
256 Hz
128 Hz
8.192 Hz
4.096 kHz
2.048 kHz
1.024 kHz
512 Hz
256 Hz
128 Hz
64 Hz
32 Hz
16 Hz
125 ms
8 Hz
250 ms
4 Hz
500 ms
2 Hz
Revision 1.1 (01-14-03)
262
SMSC LPC47N350
DATASHEET
SMSC [ SMSC CORPORATION ]
