Silicon Laboratories SI2493/57/34/15/04 - Manual (Page 119)

AN93
Rev. 1.3 119
5.7.20. U80 (Transmit Delay for V.22 Fast Connect)
U80 controls delay parameters when the modem is in V.22 Fast Connect mode (+MS=V22, AT:U7A,3) and the
server does not respond with a short answer tone prior to scrambled data or HDLC flags. U80 configures the
modem to operate without these tones. Bit 15 turns this function on. After the end of dialing, the modem waits for a
time set by U80 [14:0], then begins transmitting scrambled data (or HDLC Flags). The delay units are 1/600 s. For
example, to command the modem to begin transmitting three seconds after the end of dialing:
3 x 600 = 1800 = 0x0708. Issue command AT:U80,8708.
This register is only used when U7A[4] = 0.
Table 81. U7D Bit Map
Bit Name Function
15 Reserved Read returns zero.
14 NLM Host software recommended to always set this to bit.
0 = Enables “No Loop Current” Detect.
1 = Disables “No Loop Current” Detect.
13 Reserved Read returns zero.
12 TCAL 0 = Timed calibration disabled.
1 = Timed calibration. The time between off-hook and calibration is set in U54 (OHCT).
11 CALD 0 = No calibration during dial.
1 = Calibrate during dial. It is recommended that the dial string start with “,” to prevent first
digit loss.
10:2 Reserved Read returns zero.
1 ATZD 0 = ATZ enabled.
1 = ATZ disabled.
0 FDP 0 = FSK data processing stops when carrier is lost.
1 = FSK data processing continues for two bytes after carrier is lost.
U80 XMITDEL Transmit Delay for V.22 Fast Connect
Bit Name Function
15 V22FCDF 0 = Normal operation (default)
1 = Transmit scrambled data (or HDLC flags) after delay set in bits 14 - 0
14:0 V22FCDEL When V22FCDF = 1, V22FCDEL is the delay between end of dialing and sending
scrambled data (or HDLC flags) in 1/600 s units. Default is 0x0168 (600 ms).
When V22FCDEL = 0, V22FCDEL is the delay between ANS tone detected to start of
training.