Fujitsu F2 MC-8FX Family, Руководство по оборудованию, Страница: 521 / 602

507
CHAPTER 27 REAL TIME CLOCK
27.3.14 Frequency Fine-tuning Register (FFTR)
The Frequency Fine-tuning Register is used to fine-tune the one-second ticks.
■
Frequency Fine-tuning Register (FFTR)
Figure 27.3-15 Frequency Fine-tune register (FFTR)
The prescaler is used to divide the subclock into clocks of 0.1Hz, 1Hz, 64Hz and 1024Hz. The one-second
time ticks signal is fed into real time clock’s counters. By setting value in frequency fine-tune register, the
one-second ticks can be fine tuned.
Figure 27.3-16 Block Diagram of the Prescaler with Tuning Unit
In order to utilitize the tuning unit, user must convert the offset value into 2’s complement format first, and
set it in the frequency fine-tuning register. Offset value can range from -128(80H) to +127(7FH).
FFTR (Frequency fine-tuning register)
Address Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 Initial value
0FFD
H
FFT7 FFT6 FFT5 FFT4 FFT3 FFT2 FFT1 FFT0 XXXXXXXX
B
R/W R/W R/W R/W R/W R/W R/W R/W
Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0 offset value
1 0 0 0 0 0 0 0 -128
1 0 0 0 0 0 0 1 -127
1 1 1 1 1 1 1 1 -1
0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 1 +1
0 1 1 1 1 1 1 0 +126
0 1 1 1 1 1 1 1 +127
R/W : Readable and writable
- : Unused
X : Indeterminate
Divider f0.1Hz
Q[14] for f1Hz
32.768k Hz
Q[4] for f1024Hz
Q[8] for f64Hz
Divide-by-N*
CLK
Sub-clock
Q[15:0]
16
16-bit Prescaler
*N = 32768 + offset value in FFTR