Frequency Fine-Tuning Register (Fftr) - Fujitsu F2MC-8FX Hardware Manual

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)
FFTR (Frequency fine-tuning register)
Address Bit 7
0FFD FFT7
H
R/W
R/W : Readable and writable
- : Unused
X : Indeterminate
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
Sub-clock
32.768k Hz
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).
Figure 27.3-15 Frequency Fine-tune register (FFTR)
Bit 6 Bit 5 Bit 4
FFT6 FFT5 FFT4
R/W R/W R/W
Bit 7
1
1
1
0
0
0
0
*N = 32768 + offset value in FFTR
CLK
Divide-by-N*
16-bit Prescaler
Q[15:0]
Bit 3 Bit 2 Bit 1 Bit 0
FFT3 FFT2 FFT1 FFT0
R/W R/W R/W R/W
Bit 6 Bit 5 Bit 4 Bit 3
0 0 0 0
0 0 0 0
1 1 1 1
0 0 0 0
0 0 0 0
1 1 1 1
1 1 1 1
Q[14] for f1Hz
16
Q[8] for f64Hz
Q[4] for f1024Hz
CHAPTER 27 REAL TIME CLOCK
Initial value
XXXXXXXX
B
Bit 2 Bit 1 Bit 0 offset value
0 0 0 -128
0 0 1 -127
1 1 1 -1
0 0 0 0
0 0 1 +1
1 1 0 +126
1 1 1 +127
Divider f0.1Hz
507