Maxim Integrated 73M1822/73M1922 Control Module - Manual (Page 10)

73M1822/73M1922 Control Module User Guide UG_1x22_053
10 Rev. 1.0
2.2.1 Event Generation
During operation the driver constantly monitors the line for the following conditions:
1. APOH condition.
2. Transition back to no APOH condition (NOPOH).
3. Ring start detection.
4. End of Ring condition.
5. Battery disconnected condition.
6. Battery restored condition.
7. Polarity reversal condition.
8. Line State condition – monitoring of voltage and current.
9. Synchronization loss condition.
10. Synchronization recovered event.
11. Over voltage, Over current, or Over load condition.
12. Pulse dial complete event.
13. Pulse dial aborted event.
Section 5 provides detail descriptions of each event.
If any of these conditions occur the driver creates an event entry in the event queue and notifies the
application layer via file descriptor ready mechanism (or via file descriptor select() function). Upon
receiving this “wakeup” notification, the application can then test the file descriptor “ready” status with the
FD_ISSET
macro to confirm, and then retrieve the event from the driver via IOCTL event get command.
2.2.2 Modem Channel Configuration and Management
Configuration of the modem parameters and other management command such as hook switch operation
are done via standard device driver IOCTLs. The 73M1x22 Reference Driver provides an extended list of
IOCTLs for this purpose. The IOCTL command descriptions in
Section 6 provide details of how they
work.
2.2.3 Line State Analysis via Current and Voltage Measurements
The 73M1x22 Control Module can be programmed to provide extended line status information and line
monitoring capability. The driver operates autonomously, under the application layer control, to detect line
condition specified in pre-set criteria and automatically report status change. This alleviates the burden of
constant polling from the application layer. The line status consists of the line voltage and line current
measurements. Each measurement entity is operated independently as described below.
2.2.3.1
Interval and Even Table
The Interval and Event Table (IET) is a table that consists of multiple rows of the following information:
1. Row number.
2. Lower bound threshold.
3. Upper bound threshold.
4. Application defined event.
The application is responsible for building up the IET using the IET table update IOCTL –
M1X22_MEASURE_UPDATE
. This IOCTL can be used to create/update or to read back the current table
entry (see Section 6.6.3 for details).