Technical information

Chapter 1: Introduction to AT+i Commands
May 31, 2008 AT+i Commands Reference Manual 1-5
Internet Session Hang-up Procedure (Modem Only)
Upon completion of a dial-up Internet session, the W24 automatically executes a modem hang-up
procedure:
• The DTR line is dropped.
• After a 1second delay, W24 raises the DTR.
• If the modem responds to the DTR drop with a No Carrier then Done. Otherwise,
W24 issues a (+++) to the modem followed by ATH.
Modem Startup
Following power-up and baud rate determination, W24 in dial-up mode issues the AT<CR>
command to the modem to configure the modem's baud rate.
Analog-to-Digital Converter
W24 contains an Analog-to-Digital (A/D) 8-bit converter that receives analog input voltage
through the ADC signal. This input voltage can be monitored: if it reaches a predefined upper
threshold or goes below a certain lower threshold, an acknowledgement can be sent. This
acknowledgement is sent to the host processor through one of W24's general-purpose I/O pins
(GPIO).
Input voltage can be polled every predefined number of milliseconds. In addition, a report can be
obtained at any given time by issuing the AT+iRP19 command.
The following parameters determine the behavior of the A/D converter:
• ADCL and ADCD specify threshold and delta values, respectively. If the value read from the
register of the A/D converter is greater than the sum of ADCL and ADCD, then the GPIO pin
specified by the ADCP parameter is asserted High. If that value is less than ADCL minus
ADCD, the GPIO pin is asserted Low.
• The ADCT parameter defines an interval, in milliseconds, between consecutive queries of
the value of the A/D converter's register. W24's response time to value changes is up to
40ms.
In order to enable the A/D converter polling mechanism, you must, at the very least, set the
ADCL, ADCT, and ADCP parameters to a non-zero value.
The following table summarizes the behavior of the A/D converter.
Legend:
• R - ADC register value, which is a binary representation of the A/D converter's analog input
voltage.
• L - Base level, or threshold, as defined by the ADCL parameter.
• D - Delta, as defined by the ADCD parameter.
ADC Register Value GPIO Pin State
R > L+D
High
R < L-D Low