IBM DS-2000 warranty Functional Description Modem Status Register

				FUNCTIONAL			DESCRIPTION
	G . MODEM			STATUS	REGISTER
		+------		+
	D7		DCD	-----	Data	carrier detect
		+------		+
	D6		RI	-----	Ring	indicator
		+------		+
	D5		DSR	-----	Data set		ready
		+------		+
	D4		CTS	-----	Clear	to	send
		+------		+
	D3		DDCD	-----	Delta	data		carrier		detect
		+------		+
	D2		TERI	-----	Trailing		edge		ring	indicator
		+------		+
	D1		DDSR	-----	Delta	data		set	ready
		+------		+
	D0		DCTS	-----	Delta	clear		to	send
		+------		+
Figure 13. MODEM status register bit definitions.
DCD	-	Data Carrier Detect:
		Complement of the DCD input.
RI	-	Ring Indicator:
		Complement of the RI input.
DSR	-	Data Set Ready:
		Complement of the DSR input.
CTS	-	Clear To Send:
		Complement of			the CTS		input.

Bits DDCD, TERI, DDSR, and DCTS are the sources of MODEM status interrupts . These bits are reset when the MODEM status register is read.

DDCD - Delta Data Carrier Detect:

I n d i c a t e s t h e D a t a C a r r i e r D e t e c t i n p u t h a s changed state.

TERI - Trailing Edge Ring Indicator:

Indicates the Ring Indicator input has changed from a low to a high state.

DDSR - Delta Data Set Ready:

Indicates the Data Set Ready input has changed state.

DCTS - Delta Clear To Send:

Indicates the Clear to Send input has changed state.

iii