In figure 6, it is also possible to see the period

timing that caused the incorrect synchronization

with a timing other than that for station A to be

a sub-reception station completely separate from

station A, referred to here as station B. This IC

is thus able, in this manner, to acquire data from

both stations when the tuning is switched

between station A and station B without any

special control operations. In this case, it is

necessary for there to be temporary block

synchronization with station B, and this allows

us to apply this operation to the case of data

reception for VICS data (main station A) and

dGPS data (sub-station B). In figure 6, the

temporarily received data for station B can be

acquired as post-horizontal correction output

data, which is a real-time output, and the station

A data can be acquired as fully decoded data in

the post-vertical correction data.

• Control method

This section presents an example of a possible flow of control.

First, the application detects the frame phase difference between the VICS station and the dGPS station, and then sets

the tuning control start timing based on that phase difference. The frame synchronization forward protection count is

set to at least 3, and the block synchronization back protection count is set to 2. Since BLK_RST, which only resets the

block synchronization circuit, is used, there is no need to modify the block synchronization forward protection count.

Note that these settings can be replaced by the default settings used by this IC.

When the BLK_RST is cleared after tuning the dGPS station, the IC starts block synchronization pull in, and after the

time corresponding to the block synchronization back protection count has passed, block synchronization with the dGPS

station data will be established. The post-horizontal correction output data (data for which status bit 7 (VH) is 0) that is

output from this point will be data received from the dGPS station.

After acquiring the stipulated number of packets of data, the application sets BLK_RST valid again, and tunes back to the

VICS station. If the dGPS station reception conditions are unluckily unfavorable, it will not be possible to establish block

synchronization, or it may not be possible to acquire fully corrected packet data. However, even if such conditions occur,

the receiver must tune back to the VICS station after receiving the stipulated number of packets of data. The reason is

that if the receiver did not do so, it would become impossible to completely decode the data in vertical correction for the

VICS station itself, which is the main station being received. Since the ability of vertical correction to correct burst errors

is about 10 packets, this sequence of tuning and data acquisition operations must completed within 10 packets. If that

condition is met, it will be possible to decode the VICS station data. However, this is only possible when there are no

packets that cannot be corrected other than those missed during the sequence of the simultaneous reception processing.

No. 6166-30/33

LC72710W, 72710LW

Main

reception

station A

Incorrectly

synchronized

station

or

Sub-reception

station B

Figure 6 Main Reception Station and Sub-Reception Station