Specifications

TC35 / TC37 Hardware Interface Description
TC35_37_HD_02_V03.10 - Released Page 40 of 92 21.12.2001
3.5 Serial interface
The data interface is implemented as a serial asynchronous transmitter and receiver
conforming to ITU-T RS-232 Interchange Circuits DCE. It operates at CMOS level (2.65V).
All RS-232 signals on the ZIF connector are low active.
The GSM engine is designed for use as a DCE. Based on the conventions for DCE-DTE
connections it communicates with the customer application (DTE) using the following
signals:
• Port TxD @ application sends data to /TxD0 of the GSM engine
• Port RxD @ application receives data from /RXD0 of the GSM
Figure 14: RS-232 interface
Table 11: DCE-DTE wiring
DCE DTE
Pin no
*)
. Pin function Signal direction Pin function Signal direction
19 TxD0 Input TxD0 Output
18 RxD0 Output RxD0 Input
21 RTS0 Input RTS0 Output
20 CTS0 Output CTS0 Input
22 DTR0 Input DTR0 Output
16 DSR0 Output DSR0 Input
23 DCD0 Output DCD0 Input
17 RING0 Output RING0 Input
*)
pin numbers on ZIF connector of GSM engine
/TXD0
/RXD0
/RTS0
/CTS0
/RING0
/DCD0
/DSR0
/DTR0
/TXD0
/RXD0
/RTS0
/CTS0
/RING0
/DCD0
/DSR0
/DTR0
Siemens GSM engine
(DCE)
APPLICATION
(DTE)
Serial interface
(UART)
Serial interface
(UART)