V22 and Bell 212A Modem
CMX644A
1.4
External Components
R1
X1
100kΩ *
3.6864MHz, 7.372800MHz
or 11.0592MHz
C1, C2
C3, C4
C5
18pF
0.1µF
1µF
Resistors
±1%,
capacitors
±20%
unless otherwise stated.
*
R1 should be selected so that the IRQN pin has returned to its normal
(high) state before the CSN pin goes high.
Figure 2 Recommended External Components for Typical Application
Notes on Xtal Osc and Clock Dividers
Frequency and timing accuracy of the CMX644A is determined by the clock present at the XTAL/CLOCK pin.
This may be generated by the on-chip oscillator inverter using the external components C1, C2 and X1 of
Figure 2, or may be supplied from an external source to the XTAL/CLOCK input. If the clock is supplied from
an external source, C1, C2 and X1 should not be fitted.
The on-chip oscillator is turned off in the 'Zero-Power' mode.
If the clock is provided by an external source which is not always running, then the 'Zero-Power' mode must
be set when the clock is not available. Failure to observe this rule may cause a rise in the supply current
drawn by CMX644A.
©
2000
Consumer Microcircuits Limited
6
D/644A/6
CMLMICRO [ CML MICROCIRCUITS ]
