Wireless Modem Data Pump
FX909A
Mode Register B6: INVBIT - Invert Bits
This bit controls inversion of transmitted and received bit voltages. When set to '1' all data is inverted
in the Tx and Rx data paths so a transmitted '1' is a voltage below V at the TXOP pin and a
BIAS
received '0' is a voltage above V
is set to '1'.
at the RXIN pin. Data will be inverted immediately after this bit
BIAS
Mode Register B5: TXRXN - Tx/Rx Mode
Setting this bit to '1' puts the modem into Transmit mode, clearing it to '0' puts the modem into
Receive mode. When changing from Rx to Tx there must be a 2-bit pause before setting a new task
to allow the filter to stabilise. (See also PSAVE bit).
Note that changing between receive and transmit modes will cancel any current task
Mode Register B4: SCREN - Scramble Enable
The scrambler only takes effect during the transmission or reception of a Mobitex Data Block and
during a TSO task. Setting this bit to '1' enables scrambling, clearing it to '0' disables scrambling.
The scrambler is only operative, if enabled by this control bit, during TSO, RDB or TDB, it is held in a
reset state at all other times.
This bit should not be changed while the modem is decoding or transmitting a Mobitex Data Block.
Mode Register B3: PSAVE - Powersave
When this bit is a '1', the modem will be in a 'powersave' mode in which the internal filters, the Rx bit
and Clock extraction circuits and the Tx o/p buffer will be disabled, and the TXOP pin will be
connected to V
through a high value resistance. The Xtal Clock oscillator and the µC interface
BIAS
logic will continue to operate.
Setting the PSAVE bit to '0' restores power to all of the chip circuitry. Note that the internal filters will
take about 2 bit times to settle after the PSAVE bit is taken from '1' to '0'.
Mode Register B2: DQEN - Data Quality IRQ Enable
In receive mode, setting this bit to '1' causes the IRQ bit of the Status Register to be set to '1'
whenever a new Data Quality reading is ready. (The DQRDY bit of the Status Register will also be
set to '1' at the same time.)
In transmit mode this bit has no effect.
Mode Register B1, B0
These bits should be set to '0'.
ã 1996 Consumer Microcircuits Limited
25
D/909A/4
CMLMICRO [ CML MICROCIRCUITS ]
