Line Powered Modem plus DAA
CMX878
The state of the ICTRL pin is also dependent on the mode of the Regulator and Gyrator as shown in the
following table:
Mode of
Operation
On-hook,
min. current
On-hook,
Regulator ON
Off-hook
Programmed
Line Current
Draw
Regulator
Enabled?
N
Y
Y
Y
Gyrator
Enabled?
N
N
Y
N
DAC
Enabled?
N
N
N
Y
ICTRL
OUTPUT
Vss
Low Z Vss
Hi Z
As
programmed
on the DAC
1.5.12.7 ADC Control Register
ADC Control Register: 8-bit write-only.
C-BUS address $EE
Bit: 7 6 5 4 3 2 1 0
Register Value
The ADC comprises an 8 bit programmable reference voltage, ADC-REF, which is compared with the
voltage at the ADCIN pin. The output of the comparator is available in the Line/Wake Event Register.
The ADC is designed to operate with signals between 0V (Vss) and half supply (AVDD / 2). The external
divider will normally be configured to limit the ADCIN pin signals to within this range.
The ADC-REF voltage is:
( AVDD / 2 ) x ( Register Value / 255 )
All bits of this register are cleared to 0 by a General Reset command. A setting of all 0s will powersave
the ADC circuit and will force the output of the comparator to 1.
The ADC can be used to measure a voltage or detect a drop-out. See Section 1.5.11 for details.
© 2002 Consumer Microcircuits Limited
32
D/878/2