1200/2400bps MSK Modem for Trunked Radio Systems
4
MX429A
Pin No.
Signal
Name
Description
J/P LH
Type
9
9
D0
D1
D2
D3
10
11
12
10
11
12
Microprocessor Data Interface
These 8 lines are used by the device to communicate with a
micro-
13
13
D4
processor with the R/ W , A0 and A1 inputs determining register
selection.
14
15
16
17
14
15
16
17
D5
D6
D7
A0
Register Selection: These inputs, with the R/W input, select the
required register to the data bus as shown in Table 2
18
19
18
19
A1
Performs the dual functions of selecting the device for Read or
Write and strobing data in or out. It should be generated by gating
the high order address bits with a Read/Write clock. The MX429A
is selected when this pin is a logic ‘0’.
STROBE
20
21
20
21
Used in conjunction with A1 and A0 to determine which internal
registers are connected to the data interface pins (D0 to D7)
during Strobe.
R/ W
IRQ
Interrupt Request. This line will go to a logic '0' when an interrupt
occurs. This output can be "wire OR'd" with other active low
components (100kW pullup to V ). The conditions that cause
DD
the interrupts are indicated at the Status Register and are as
follows: Timer Expired, Rx Data Ready, Tx Data Ready, Tx Idle,
Rx SYNC Detect, Rx SYNT Detect
22
24
A logic ‘1’ on this pin selects the 1200 baud option. Tone
frequencies are: one cycle of 1200Hz represents a logic ‘1’, one
and a half cycles of 1800Hz represents a logic ‘0’.
A logic ‘0’ on this pin selects the 2400 baud option. Tone
frequencies are: one half cycle of 1200Hz represents a logic ‘1’,
one cycle of 2400Hz represents a logic ‘0’. This pin has an
internal 1Mꢁ pullup resistor.
1200/2400 Baud
Select
23
24
22
23
V
Power Negative Supply (GND)
SS
Clock/4
A 1.008 MHz (X1 ÷ 4) clock is available at this output for external
circuit use, note the source impedance and source current limits.
Leave this pin open-circuit
4
3
Table 1: Signal List
Register
Control
R/
A0
1
A1
1
W
0
Status
1
1
0
1
1
1
1
Rx Data
0
1
Tx Data
0
1
Syndrome Low
Syndrome High
0
0
1
0
Table 2: Register Selection
© 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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