1200/2400bps MSK Modem for Trunked Radio Systems
5
MX429A
3 External Components
VDD
VBIAS
CLOCK/4
VSS
1
2
3
4
5
6
7
24
23
22
21
20
19
18
TRANSMIT OUTPUT
RECEIVE INPUT
1200/2400 BAUD SELECT
C4
C5
C3
IRQ
R/W
VDD
'CD' TIME CONSTANT
XTAL/CLOCK
STROBE
A1
R2
C6
A0
D7
D6
D5
D4
XTAL
D0
8
17
16
15
14
13
9
D1
10
11
12
D2
D3
Recommended Xtal
Component
Xtal/Clock
7
X1
R1
MX429A
8
C1
C2
XTAL
D0 D1 D2 D3 D4 D5 D6 D7
MICROPROCESSOR DATA INTERFACE
Figure 2: Recommended External Components
R1
R2
C1
C2
C3
C4
C5
C6
1Mꢁ
1Mꢁ
33pF
33pF
0.1ꢃF
ꢂ10%
ꢂ10%
ꢂ20%
ꢂ20%
ꢂ20%
1.0ꢃF
1.0ꢃF
1.0ꢃF
ꢂ20%
ꢂ20%
ꢂ20%
X1
Note 1
4.032MHz
Table 3: Recommended External Components
Notes:
1. For best results, a crystal oscillator design should drive the clock inverter input with signal levels of at
least 40% of VDD, peak to peak. Tuning fork crystals generally cannot meet this requirement. To
obtain crystal oscillator design assistance, consult your crystal manufacturer.
© 1998 MX-COM Inc.
www.mxcom.com Tel: 800 638-5577 336 744-5050 Fax: 336 744-5054
Doc. # 20480128.007
4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
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