Silicon Laboratories SI2493/57/34/15/04 Synchronous Mode, = Normal asynchronous mode, Given time

AN93

			Table 79. U7A Bit Map (Continued)
Bit	Name		Function
1	HDLC	Synchronous Mode.
		0	= Normal asynchronous mode.
		1	= Transparent HDLC mode.*
0	FAST	Fast Connect. This bit is mutually exclusive with bit 4; only one bit can be enabled at a
		given time.
		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.

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 pin when U7C [0] (RIGPOEN) = 1. This allows the RI pin to be configured as a general-purpose output pin under host processor control. The RI pin must not pulled down. Doing so forces the modem to enter an undocumented emulation mode.

Bit 0 (RIGPOEN)=0 (default) allows the RI pin to indicate a valid ring signal. When Bit 0 = 1, RI outputs the value of RIGPO (See Table 80).

U7D is a bit-mapped register with bits 15,13:9, and bits 8:2 reserved. U7D resets to 0x4001 with a power-on or manual reset.

Bit 14 (NLM) = 0 (default) causes the modem to automatically detect loop current absence or loss. When bit 14 = 1, this feature is disabled.

Bit 12 (TCAL) = 0 (default) when set to 1 forces the DAA to calibrate at a programmable time after going off-hook. The time between going off-hook and the start of calibration is programmed with U54 [15:8] in 32 ms units.

Bit 11 (OHCT) = 0 (default) when set to 1 forces the DAA to calibrate at the start of dialing. The first dial character should be a delay (“,”) to prevent interference with the first digit.

Bit 1 (ATZD) = 0 (default) allows the ATZ command to be active. When Bit 1 = 1, the ATZ command is disabled.

Bit 0 (FDP) = 0 (default). FSK data processing stops when the carrier is lost. Unprocessed data are lost. Setting Bit 0 = 1 causes FSK data processing to continue for up to two bytes of data in the pipeline after carrier is lost.

						Table 80. U7C Bit Map
Bit	Name					Function
15:5	Reserved	Read returns zero.
4	RIGPO	RI		pin
		Follow this bit when U7C [0] (RIGPIOEN) = 1.
3:1	Reserved	Read returns zero.
0	RIGPOEN	0	=		RI	pin indicates valid ring signal.
		1	= RI pin follows U7C [4] (RIGPO).

118 Rev. 1.3