V.23 Compatible Modem
FX604
1.4
External Components
R1
X1
100k
Ω
3.579545MHz
C1, C2
C3
C4
18pF
0.1
µ
F
0.1
µ
F
Resistors
±
5%, capacitors
±
10% unless otherwise stated.
Figure 2 Recommended External Components for Typical Application
1.5
1.5.1
General Description
Xtal Osc and Clock Dividers
Frequency and timing accuracy of the FX604 is determined by a 3.579545MHz 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 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 significant rise in the supply
current drawn by FX604 as well as generating undefined states of the RXD, DET and RDYN outputs.
©
1996 Consumer Microcircuits Limited
5
D/604/3