Service manual

DATA INTERFACE DESCRIPTION
A-2
April 2001
Part No. 001-9800-203
Receive Audio Signals
The two receive audio signals which follow are selected by installing either R357 or R361 on the audio/logic board.
Only one resistor can be installed at a time. The receive audio line is called “Rx Filt Out” on the schematic.
Rx Filt Out J301- 2 This output signal is selected by installing R361 and removing R357. It provides a bandpass filtered
and de-emphasized receive audio signal that is shared with the internal option slots. Its characteris-
tics are as follows: AC coupled 300 to 3000 Hz TIA, Output Impedance = 1k ohms, Level = 1.7 V
p-p at 60% system deviation.
Rx Demod
Out
J301-2 This output signal is selected by installing R357 and removing R361. It provides a buffered unfil-
tered discriminator output signal that is shared with the internal option slots. Its characteristics are
as follows: DC coupled (2.8 VDC reference) DC to 5 kHz +1 –3 dB, Output Impedance = 1k ohms,
Level = 1 V p-p at 60% system deviation.
Transmit Audio Signals
The two transmit audio signals which follow are selected by installing either R398 or R399 on the audio/logic board.
Only one resistor can be installed at a time. The transmit audio line is called “Tx Filt In” on the schematic.
Tx Filt In J301-3 This input signal is selected by installing R398 and removing R399. It bypasses the high-pass filter
but still goes through the low-pass splatter filter and undergoes pre-emphasis and deviation limiting.
The device producing this signal must provide a means of adjusting deviation externally. The char-
acteristics of this signal are as follows: AC coupled 4 Hz to 3 kHz, Input Impedance = Greater than
10k ohms, Level = 1 V p-p typical for 60% system deviation.
Tx WB In J301-3 This input signal is selected by installing R399 and removing R398. It bypasses splatter filtering,
pre-emphasis, and deviation limiting circuitry, and so provides a direct modulation port. The device
producing this signal must provide a means of adjusting deviation externally. In addition, it must
provide FCC approved deviation limiting and splatter filter circuitry. The user assumes responsi-
bility for FCC approval when this line is used. The characteristics of this signal are as follows:
DC coupled 0 Hz to 4800 Hz, Input Impedance = Greater than 10k ohms, Level = 1 V p-p typical
for 60% system deviation, DC coupling requires 2.5 VDC ±2% reference.
Input Control Signals
All of the following input control lines are CMOS inputs that are pulled high internally (to 5V) with 10k-ohm resistors.
None of these inputs are equipped for switch debounce, so that must be provided if applicable. All except Ext Serv Req can
be programmed either active high or low. These lines are programmed as described in Section 4.9 for the functions described
in Table A-2.
In 2 J301-7 Programmable input.
In 3 W301 Programmable input.
Ext Serv
Req
J301-8 This line is not programmable and is always active low.
PTT W302/W312 This line is not programmable and is always active low (low state keys transmitter).
Option 1 J301-9 Programmable as either an input or output. When programmed as an input and a state change
occurs, microprocessor interrupts are produced. All I/O lines are then checked for state changes.
This allows a signal such as “Data PTT” to get a rapid response.
Output Control Signals
Unless noted otherwise, all of the following input control lines are 5-volt CMOS outputs with a 470-ohm output imped-
ance and capable of sourcing 10 mA maximum. All, except when noted otherwise, can be programmed either active high or
low. These lines are programmed as described in Section 4.9 for the functions described in Table A-2.
Output A W309 Programmable output.
Output B W319 Programmable output.
Output C J301-10 Programmable output.
Output D J101-3 Programmable output.
Table A-1 Data Interface Line Electrical Specifications (Continued)
Name Origin Description