LC72705 View Datasheet(PDF) - SANYO -> Panasonic
Part Name
Description
Manufacturer
LC72705 Datasheet PDF : 14 Pages
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Layer 4 CRC Data Input Timing
LC72705E
CRC4 pin output
CRC4 output after N items transferred
Note: The N items are 8-bit units.
Serial Control Data Input Settings
The input data consists of 16 bits (DI0 to DI15). The upper 8 bits (DI8 to DI15) are the control address and the lower 8
bits (DI0 to DI7) are the input data. Bits DI12 to DI15 are ignored.
Register
Number of allowable BIC errors
Address
DI11 DI10 DI9 DI8
0
0
0
0
Number of block error protection states
0
0
0
1
Number of frame error protection states
0
0
1
0
Control register
0
0
1
1
Data
Upper 4 bits
Allowed error bits backward
Lower 4 bits
Allowed error bits forward
Upper 4 bits
Block backward protection
Lower 4 bits
Block forward protection
Upper 4 bits
Frame backward protection
Lower 4 bits
Frame forward protection
See the control register description on page 8
Default setting
2
2
1
7
1
7
• Number of allowed BIC errors
This IC’s synchronization circuit operates by recognizing a 16-bit BIC code. The number of allowed errors is the
number of allowed error bits in the 16 bits used for BIC recognition. This data item allows the forward protection mode
(used when synchronized) and the backward protection mode (used when not synchronized) values to be set
independently. The default value is to allow up to 2 error bits in both the forward and backward directions. We
recommend setting the backward protection mode number of allowable BIC errors to 1 or 0 if the block
synchronization recognition output (the BLOCK pin, pin 23) is used to recognize the presence or absence of FM
multiplex data.
• Block synchronization errors protection count
The synchronization protection count can be set independently in the forward and backward directions. The protection
count conditions are as follows.
— Backward protection (unsynchronized, BLOCK = low)
When the timing of the IC’s internal synchronization free-running counter matches that of the received BIC, the
protection count is incremented by 1. Similarly, if the IC internal counter and the received BIC do not match, the
counter is cleared to 0. The count timing is the timing of the IC internal counter.
— Forward protection (synchronized, BLOCK = high)
Operation is the opposite of the backward case, namely, the protection count is incremented when the timing of the
IC’s internal synchronization free-running counter does not match that of the received BIC, and the protection
count is cleared to zero when the timing matches.
Figure 1 shows the protection counter when both the forward and backward protection counts are set to 3. This IC
defines the protection counter value to be 1 at the point where a match or a mismatch occurs between the IC
internal timing and the received BIC timing. For example, a backward protection count of 2 corresponds to the case
where the IC internal timing and the received BIC timing match two times consecutively. To set the protection data
to new values, applications must send data in which 1 has been subtracted from the desired values, e.g. to set up
protection counts of 3 as shown in figure 1, applications must send the value 22H. Similarly, if the value set is 00,
due to the definition, the protection counts for both the forward and backward directions will be set to 1. However,
from an operation standpoint, this corresponds to operation equivalent to there being no protection circuit. The
default values are a forward protection count of 8 and a backward protection count of 2. We recommend resetting
the block synchronization backward protection count to a value more strict than the default, e.g. to a value of 3 or
more as opposed to the default of 2, if the block synchronization recognition output (the BLOCK pin, pin 23) is
used to recognize the presence or absence of FM multiplex data.
No. 5744-6/14
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