Tait TM8000 Series, Applications Manual

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TM8000 3DK Hardware Developer’s Kit Application Manual Programmable I/O Lines 65
September 2003 © Tait Electronics Ltd
Output Circuitry
The digital outputs are designed to interface to application circuitry in a
straightforward manner.
Figure 3.9 shows a simplified diagram of the digital
output lines (ESD protection not shown). For full details of the interface,
refer to the PCB information chapter of the TM8100 Mobile Radio Service
Manual or the technical support website.
The internal logic circuitry of the radio operates at 3.3V. Unless application
circuitry is able to operate at this voltage level, some form of level conversion
will normally be required. With the AUX and CH output lines, conversion
to 5 V or 13.8 V can be selected by moving the pullup resistor as indicated
in
Figure 3.9 .
Note
These resistors only provide a weak pullup and hence the output
is only able to source a very small current. In the logic low state,
the outputs can sink a higher current. For more information refer
to
“Description of the Radio Interfaces” on page 15 .
The IOP output lines always operate at 3.3V logic levels and any level
conversion is the responsibility of the application circuit designer.
Figure 3.9 Digital output lines - simplified circuit diagrams
4.7k
AUX_GPIO4…7
a
+3.3V
1k
33k
IOP_GPIO1…7
4.7k
+3.3V
100k
+3.3V +5V
*
+13.8V
*
a. With AUX_GPIO4…7, the
33k
Ω
resistor can be
moved to change the logic
high output voltage to +5V
or +13.8V.
56
33k
*
CH_GPIO1