Specifications

AN93
Rev. 0.9 95
3.3.44. U7A (GENA)
U7A is a bit-mapped register. U7A resets to 0x0000.
Bits 15:8 and 5:3 are reserved.
Bit 7 (DOP) is used in a method to determine whether a
phone line supports DTMF or pulse only dialing. See
"3.5.11. Pulse/Tone Dial Decision" on page 125 for
details.
Bit 6 (ADD) attempts DTMF dial, then falls back to pulse
dialing if unsuccessful. First digit is dialed as DTMF. If a
dial tone is still present after two seconds, the Si2493/
57/34/15/04 redials the first digit and remaining digits as
pulse. If a dial tone is not present after two seconds, the
Si2493/57/34/15/04 dials the remaining digits as DTMF.
Bit 1 (HDLC) controls whether the normal asynchronous
mode (default) is used or the transparent HDLC mode is
enabled. See "3.1.6. Legacy Synchronous DCE Mode/
V.80 Synchronous Access Mode" on page 23 for more
details on these modes.
Bit 0 controls whether the normal ITU/Bellcore modem
handshake (default) or a special fast connect
handshake is used. Fast connect is typically used in
specialized applications, such as point-of-sale
terminals, where it is important to rapidly connect and
transfer a small amount of data (see Table 66).
3.3.45. U7C (GENC)
U7C is a bit-mapped register with bits 15:5 and bits 3:1
reserved. U7C resets to 0x0000 with a power-on or
manual reset.
Bit 4 (RIGPO) is output on RI (Si2493/57/34/15/04
pin 15) when U7C[0] (RIGPOEN) = 1
b
. This allows the
RI pin to be configured as a general-purpose output pin
under host processor control.
Bit 0 (RIGPOEN)=0 (default) allows RI (Si2493/57/34/
15/04 pin 15) to indicate a valid ring signal. When Bit
0=1
b
, RI outputs the value of RIGPO. (See Table 67.)
Table 65. U79 Bit Map
Bit Name Function
15:6 Reserved Read returns zero.
5:0 LVCS Line Voltage Current Sense.
On-Hook = Voltage Monitor (2.75 V/bit).
Off-Hook = Loop Current Monitor (3 mA/bit).
Table 66. U7A Bit Map
Bit Name Function
15:8 Reserved Read returns zero.
7DOP0 = Normal ATDTW operation.
1 = Use ATDTW for pulse/tone dial detection (see "3.5.11. Pulse/Tone Dial Decision" on page
125 for details).
6ADDAdaptive Dialing.
1 = Enable
0=Disable
5:3 Reserved Read returns zero.
2 Reserved Read returns zero.
1HDLCSynchronous Mode.
0 = Normal asynchronous mode.
1 = Transparent HDLC mode.*
0 FAST Fast Connect.
0 = Normal modem handshake timing per ITU/Bellcore standards.
1 = Fast connect modem handshake timing.*
*Note: When HDLC or FAST is set, the \N0 (Wire mode) setting must be used.