Telit Communications S.p.A. GE864Q2B ユーザーズマニュアル
GE864
GE864
GE864
GE864----QUAD V2 / GE864
QUAD V2 / GE864
QUAD V2 / GE864
QUAD V2 / GE864----DUAL V2 Hardware User Guide
DUAL V2 Hardware User Guide
DUAL V2 Hardware User Guide
DUAL V2 Hardware User Guide
1vv0300875 Rev.1 – 2010-03-29
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved.
Page 39 of 73
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For a minimum implementation, only the TXD and RXD lines can be connected, the
other lines can be left open provided a software flow control is implemented.
other lines can be left open provided a software flow control is implemented.
9.2.
9.2.
9.2.
9.2.
RS232 L
RS232 L
RS232 L
RS232 Level
evel
evel
evel T
T
T
Translation
ranslation
ranslation
ranslation
In order to interface the Telit GE864-QUAD V2 / GE864-DUAL V2 with a PC com port
or a RS232 (EIA/TIA-232) application a level translator is required. This level
translator must
or a RS232 (EIA/TIA-232) application a level translator is required. This level
translator must
•
invert the electrical signal in both directions
•
change the level from 0/+3V to +15/-15V
Actually, the RS232 UART 16450, 16550, 16650 & 16750 chipsets accept signals with
lower levels on the RS232 side (EIA/TIA-562), allowing for a lower voltage-multiplying
ratio on the level translator. Note that the negative signal voltage must be less than
0V and hence some sort of level translation is always required.
lower levels on the RS232 side (EIA/TIA-562), allowing for a lower voltage-multiplying
ratio on the level translator. Note that the negative signal voltage must be less than
0V and hence some sort of level translation is always required.
The simplest way to translate the levels and invert the signal is by using a single chip
level translator. There are a multitude of them, differing in the number of driver and
receiver and in the levels (be sure to get a true RS232 level translator not a RS485 or
other standards).
level translator. There are a multitude of them, differing in the number of driver and
receiver and in the levels (be sure to get a true RS232 level translator not a RS485 or
other standards).
By convention the driver is the level translator from the 0/+3V UART level to the
RS232 level, while the receiver is the translator from RS232 level to 0/+3V UART.
RS232 level, while the receiver is the translator from RS232 level to 0/+3V UART.
In order to translate the whole set of control lines of the UART you will need:
•
5 driver
•
3 receiver
NOTE:
NOTE:
NOTE:
NOTE:
The digital input lines working at 2.8VCMOS have an absolute maximum input voltage
of 3,1V; therefore the level translator IC shall not be powered by the +3.8V supply of
the module. Instead it shall be powered from a +2.8V / +3.0V (dedicated) power
supply.
This is because in this way the level translator IC outputs on the module side (i.e.
GE864-QUAD V2 / GE864-DUAL V2 inputs) will work at +3.8V interface levels,
stressing the module inputs at its maximum input voltage.
This can be acceptable for evaluation purposes, but not on production devices.
of 3,1V; therefore the level translator IC shall not be powered by the +3.8V supply of
the module. Instead it shall be powered from a +2.8V / +3.0V (dedicated) power
supply.
This is because in this way the level translator IC outputs on the module side (i.e.
GE864-QUAD V2 / GE864-DUAL V2 inputs) will work at +3.8V interface levels,
stressing the module inputs at its maximum input voltage.
This can be acceptable for evaluation purposes, but not on production devices.