Wireless Modem Data Pump
FX909A
1.5.4.6 Data Quality Register
This is intended to indicate the quality of the receive signal during a Mobitex Data Block or 30 single
bytes. In receive mode, the modem measures the 'quality' of the received signal by comparing the
actual received zero crossing time against an internally generated time. This value is averaged over
240 bits and at the end of the measurement the Data Quality Register and the DQRDY bit in the
Status Register is updated. Note: An interrupt will only occur at this time if the DQEN bit = '1'.
To provide synchronisation with Data Blocks, and hence ensure the Data Quality Register is updated
in preparation to be read when the RDB task finishes, the measurement process is reset at the end
of tasks SFH, SFS, RDB and R3H.
In transmit mode all bits of the Data Quality Register will be '0'.
Figure 12 shows how the value (0-240) read from the Data Quality Register varies with received
signal to noise ratio.
Figure 12 Typical Data Quality Reading (after 240 bits) vs S/N, (noise in bit rate bandwidth)
ã 1996 Consumer Microcircuits Limited
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D/909A/4
CMLMICRO [ CML MICROCIRCUITS ]
