Cinterion
®
ELS31-VA/ELS51-VA Hardware Interface Description
2.1 Application Interface
56
ELS31-VA_ELS51-VA_HID_v01.000
2017-01-04
Confidential / Preliminary
Page 25 of 106
2.1.4
Serial Interface ASC0
ELS31-VA/ELS51-VA offers an 8-wire unbalanced, asynchronous modem interface ASC0 con-
forming to ITU-T V.24 protocol DCE signalling. The electrical characteristics do not comply with
ITU-T V.28. The significant levels are 0V (for low data bit or active state) and 1.8V (for high data
bit or inactive state). For electrical characteristics please refer to
. For an illustration of
the interface line’s startup behavior see
.
ELS31-VA/ELS51-VA 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 the module’s TXD0 signal line
•
Port RXD @ application receives data from the module’s RXD0 signal line
Figure 6:
Serial interface ASC0
Features:
•
Includes the data lines TXD0 and RXD0, the status lines RTS0 and CTS0 and, in addition,
the modem control lines DTR0, DSR0, DCD0 and RING0.
•
Configured for 8 data bits, no parity and 1 stop bit.
•
ASC0 can be operated at fixed bit rates from 4800bps up to 921600bps.
•
Supports RTS0/CTS0 hardware flow control. Communication is possible by using only RXD
and TXD lines, if RTS0 is pulled low.
•
Wake up from SLEEP mode by RTS0 activation (high to low transition; see
).
The ASC0 interface is dedicated to signaling via AT commands (3GPP standard 27.007 + mod-
ule specific AT commands).
Note: The ASC0 modem control lines DTR0, DCD0, DSR0 and RING0 can also be configured
as GPIO lines. If configured as GPIO lines, these GPIO lines are assigned as follows:
DTR0 --> GPIO1, DCD0 --> GPIO2, DSR0 --> GPIO3 and RING0 --> GPIO24.
