User's Manual

GC864 Hardware User Guide
1vv0300733 Rev. 0 - 12/06/06
Reproduction forbidden without Telit Communications S.p.A. written authorization - All Right reserved page 27 of 68
NOTE: The UART input line TXD (rx_uart) of the GC864 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 VAUX pad, whose absolute maximum output current is 100mA.
Pull-up resistors can be connected to the VAUX pad provided that the pulled-up lines are GC864 input
lines connected to open collector outputs in order to avoid latch-up problems on the GC864.
Care must be taken to avoid latch-up on the GC864 and the use of this output line to power electronic
devices shall be considered with care, especially for devices that generate spikes and noise such as
level translators, digital ICs or microcontroller, failure in any of these condition can severely
compromise the GC864 functionality.
NOTE: The input lines working at 2.8VCMOS can be pulled-up with 47KΩ resistors that can be
connected directly to the VAUX line.
NO disturbing devices should be powered with the VAUX line, otherwise the module
functionality may be compromised.