TEA6100 Philips Semiconductors (Acquired by NXP), TEA6100 Datasheet - Page 24

• Manufacturer Part Number: TEA6100
• Description: TEA6100; Fm/if System And Microcomputer-based Tuning Interface
• Manufacturer: Philips Semiconductors (Acquired by NXP)

Philips Semiconductors
PROGRAMMING INFORMATION
Converting the read out of the counters into frequency
The counter resolution at the input is defined as:
For every increment of the counter the counted frequency increases relative to the resolution in Hertz, as shown in
example:
The counter consists of 8 bits. Therefore, the maximum frequency range that can be counted is
256
overflow (in the example above, 7 times). The real measured frequency is:
The overflow indicates the off-set on the frequency scale which must be added to the read out. Due to the bandwidth of
the IF filter, the frequencies at the input to the TEA6100 are known, for example:
The read out of the counter has to be translated into frequency. This translation depends upon the counter resolution.
The preferred way to calculate the input frequency is to:
The formulae for calculating the target IF read out and the resolution are as follows (A, D, E, F and G refer to the bits of
the I
and Gn are inverted values of the variables A, D, E, F and G. Table 3 shows the following formulae calculated for a
reference frequency of 40 kHz):
Note
Care should be taken if TIFF
or if TIFF
August 1987
resolution = divider ratio of N2/window
window = 20 ms; N2 = 128; IF frequency = 10,7 MHz; resolution = 128/0,02 = 6,4 kHz per count
f
IF filter for FM has a center frequency of 10,7 MHz and 3 dB bandwidth of 300 kHz. Only the frequencies of 10,7 MHz
calculate the read out of the target IF frequency. Compare this value with that of the measured read out and multiply
the difference by the resolution.
N1 = (An
Window (T) = N1/F
N2 = (E
Target decimal read out (TDEC) = T
Target read out hexadecimal (THEX), convert the target decimal read out to hexadecimal and use the 2 least
significant digits (Do not use overflow value). The symbol for measured hexadecimal is MHEX
Resolution (R) = N2/T
Measured frequency (F
Counter accuracy (AW and AN), with bit 7 (G) the accuracy can be chosen with the same resolution. If bit 7 is logic 1
the accuracy is HIGH and if bit 7 is logic 0 then the accuracy is LOW.
bit 7 = 0, AN =
bit 7 = 1, AW =
FM/IF system and microcomputer-based
tuning interface
real
2
150 kHz occur at the input of the TEA6100. For this reason it is not necessary to count the overflow.
C bus input data as shown in Fig.3 and 4 and to the counter/timer block diagram shown in Fig.6. An, Dn, En, Fn
resolution = 1,6384 MHz. In the example the frequency to be counted is 10,7 MHz, therefore, the counter will
= (read out
1
16
2
4
filter bandwith is less than the frequency at read out for hexadecimal value 00.
A
8
(N2/T)
overflow
(
1
En
5)
ref
2
N2/T)
I
(En
) = (TIFF)
[Dn
1
256)
4
2
1 D
filter bandwidth is greater than the frequency for the read out of hexadecimal value FF,
E
resolution
R
5)
16])
(TIFF/N2
(MHEX
8
(G
(2
[E
2
THEX).
(E
2
Gn
G
247
24
1]
1)
)
En
(F
79). TIFF is the symbol for target IF frequency
1
Fn
8)
Product specification
TEA6100