Rainbow Electronics GM862-QUAD-PY - Manual (Page 35)

GM862-QUAD / PY Hardware User Guide
1vv0300748 Rev. 5 - 20/09/07
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Rights Reserved page 35 of 68
NOTE: The UART input line TXD (rx_uart) of the GM862-QUAD / PY is NOT internally pulled up with a resistor, so
there may be the need to place an external 47KΩ pull-up resistor, either the DTR (dtr_uart) and RTS (rts_uart) input
lines are not pulled up internally, so an external pull-up resistor of 47KΩ may be required.
A power source of the internal interface voltage corresponding to the 2.8VCMOS high level is
available at the PWRMON pin on the connector, whose absolute maximum output current is 1mA.
A maximum of 9 resistors of 47 KΩ pull-up can be connected to the PWRMON pin, provided no other
devices are connected to it and the pulled-up lines are GM862-QUAD / PY input lines connected to
open collector outputs in order to avoid latch-up problems on the GM862-QUAD / PY.
Care must be taken to avoid latch-up on the GM862-QUAD / PY and the use of this output line to
power electronic devices shall be avoided, especially for devices that generate spikes and noise such
as switching level translators, micro controllers, failure in any of these condition can severely
compromise the GM862-QUAD / PY functionality.
NOTE: The input lines working at 2.8VCMOS can be pulled-up with 47KΩ resistors that can be connected directly to
the PWRMON line provided they are connected as in this example.
NO OTHER devices than those suggested should be powered with the PWRMON line; otherwise the module
functionality may be compromised.
It is important to consider that the added circuit must have consumption lower than 1mA.
In case of reprogramming of the module has to be considered the use of the RESET line to start correctly the
activity.
The preferable configuration is having an external supply for the buffer.