Intel MD566X - Manual (Page 51)

56K V.92 Data, Fax, and Voice Chipset
Programmer’s Guide Intel Confidential 51
&Dn 2
DTR (Data Terminal Ready) Option: This command controls how the mo-
dem responds to DTR. After toggling DTR, the host should wait 200 ms be-
fore modifying the UART registers or sending a new command to the mo-
dem. This is done because the modem does not send an “OK” message to
indicate it has performed the requested function.
n = 0 In asynchronous mode (&Q0), the modem ignores DTR.
n = 1 The modem switches from data mode to command mode when an
on-to-off transition of DTR occurs.
n = 2** An on-to-off transition of DTR causes the modem to go on-hook
(hang up). While DTR is off, auto-answer is disabled.
n = 3 An on-to-off transition of DTR re-initializes the modem. The re-ini-
tialize procedure performs the same function as a power-up reset,
except that the UART registers are not reconfigured.
&F none
Load Factory Defaults: This command loads command defaults and S-reg-
ister factory defaults into the active configuration and configures the modem
for data mode.
&Gn 0
Guard Tone Option: This command controls whether the modem sends out
guard tones while connected to a remote modem (for ITU-T V.22 bis
[1200 bps] and V.22 bis [2400 bps] connections only). Guard tones may be
required in some countries but are not needed in the United States. Guard
tones are sent by the answer modem to disable Central Office echo cancel-
ers.
n = 0** Guard tone disabled
n = 1 550-Hz guard tone enabled
n = 2 1800-Hz guard tone enabled
&Kn 3
Select Serial Port Flow Control: This command specifies the DTE-to-modem flow
control. Software flow control uses the characters XOFF (13h) and XON (11h) to
stop and start data transmission, respectively, both to and from the DTE. Bidirection-
al hardware flow control uses RTS/CTS to stop and start data from the modem.
n = 0 Disables flow control
n = 3** Bidirectional hardware flow control — RTS/CTS
n = 4 XON/XOFF software flow control
&M0 0
Select Communication Mode: This command controls whether the modem
operates in asynchronous or synchronous mode. This modem only supports
asynchronous mode. This command is the same as &Q0.
n = 0** Asynchronous normal. The modem operates asynchronously in
both command and online modes.
Table 3-4. Data Mode Command Descriptions (Continued)