User Manual

GM47/48 Technical description

BA/SEM/MS 02:0004 Rev B

3.10.3 Control Signals - RTS, CTS, DTR, DCD, RI

The control signals are active low, and hence when a standard

interface IC is used (such as MAX3237), then standard RS-232 levels

are obtained.

These signals together with DGND, RD and TD form a 9-pin RS-232

data port (with the exception of the voltage levels and DSR).

RTS and CTS shall be capable of transmitting at 1/10 of the data

transmission speed for data rates, up to 460 kbit/s. (Byte oriented flow

control mechanism).

Switching times for RTS and CTS

Parameter Limit

Time from Low to High level < 2 µs

Time from High to Low level

< 2 µs

Request to Send (RTS)

RTS is an input to the module. The signals on this circuit shall be used

to condition the DCE (the module when used for data transmission

purposes) for data transmission. Default level is OFF, by internal pull

up.

The exact behaviour of RTS shall be defined by an AT command.

Software or hardware flow control can be selected. Hardware flow

control is the default.

This is a Dig. 2.75 CMOS Input and general characteristics are

applicable.

It is the duty of the application to pull RTS low (logic levels) to

request communications with the module. The module will respond by

asserting CTS low and as such may be used as a notification as a

module status ready for communication.

Parameter Limit

Application driving impedance

< 100 Ω

Input capacitance < 2 nF

Input resistance (pull-down)

100 kΩ to DGND