Z02215
Single Chip Modem with Integrated Controller, Data Pump, and AFE
45
Alternatively, the user can select the \R1command option and use the RTShard-
ware signal to initiate a line reversal. When RTSchanges from active (logic 0or 0
volts) to inactive (logic 1or +5 volts), the line turnaround executes. This method is
the fastest method of executing the line turnaround.
At execution of the Rcommand, the CarrierDetectsignal (CD) goes inactive, the
modem reverses (its carrier changes from 390 Hz to 1300 Hz), and waits for a 390
Hz carrier for 440 ms.
•
If the modem detects more than 40 ms of a 390 Hz carrier within 440 ms, it
sends the CONNECT1200/75result code to the Host. CD goes active.
•
If the modem does not detect more than 40 ms of a 390 Hz carrier within 440
ms, it hangs up and sends the NO CARRIERcode to the Host.
Reverse Turnaround
The modem performs a Reverse turnaround when a carrier drop longer than 20
ms is detected. The CarrierDetect(CD) signal goes inactive and the modem
reverses its carrier (from 1300 Hz to 390 Hz) and waits for a 1300 Hz carrier for
220 ms.
•
If the modem detects more than 40 ms of a 1300 Hz carrier within 220 ms, it
sends the CONNECT 75/1200code to the Host. The CD then goes active.
•
If the modem does not detect more than 40 ms of a 1300 Hz carrier within 220
ms, it reverses again and waits for a 390 Hz carrier for 220 ms.
–
If the modem detects more than 40 ms of a 390 Hz carrier within 220 ms, it
sends the CONNECT 1200/75code to the Host. The CDthen goes active
(there was a short carrier dropout).
–
If the modem does not detect more than 40 ms of a 390 Hz carrier within
220 ms, it hangs up and sends the NO CARRIERcode to the Host.
If the modem is in REVERSE mode and receives the R command, it sends the
ERRORcode to the Host.
STATIC REVERSE Mode
If the command ATR has been executed, the following ATD command forces the
modem to try to connect in REVERSE mode.
Escape Sequences
An escape sequence is one or more particular characters sent from the terminal to
the modem during the ON-LINE state. This sequence is activated to switch the
PS001907-0904
Escape Sequences
ZILOG [ ZILOG, INC. ]
