Neo_M660A GPRS Module Hardware User Guide
Copyright © Neoway Technology Co., Ltd
20
Figure 3-16
RING indicator for incoming call
4 s
250 ms
250 ms
SMS: Upon receipt of SMS, the module outputs one 600 ms low pulse.
Figure 3-17
RING indicator for SMS
600 ms
3.5
SIM Card Interface
Table 3-5
SIM card interface
Pin Name
I/O
Function Description
Remarks
VSIM
P
SIM card power supply output
1.8/3.0V
SIM_CLK
DO
SIM card clock output
SIM_RST
DO
SIM card reset output
SIM_DATA
DI/O
SIM card data IO
With internal pull-up resistor
M660A supports 3.0 V and 1.8 V SIM cards. VSIM supplies power for SIM card at Max. 30 mA.
SIM_DATA is pulled up by an internal resistor. You do not have to add and external pull-up resistor in your
design.
SIM_CLK can work at several frequencies at 3.25 MHz typically. SIM card is sensitive to GSM TDD noise
and RF interference. So, the PCB design should meet the following requirements:
The antenna especially build-in antenna should be installed a long distance away from the SIM card
and SIM card traces.
The PCB traces of SIM should be as short as possible and shielded with GND copper.
