SMSC COM20020 manual DIP PIN Plcc PIN Name Symbol Description, Transmission Media Interface

DIP PIN	PLCC PIN	NAME
NO.	NO.		SYMBOL	DESCRIPTION
19	23	nReset in	nRESET IN	Input. This active low signal issued by the
				microcontroller executes a hardware reset.
				It is used to activate the internal reset
				circuitry within the COM20020.
20	24	nInterrupt	nINTR	Output. This active low signal is generated
				by the COM20020 when an enabled
				interrupt condition occurs. nINTR returns to
				its inactive state when the interrupt status
				condition or the corresponding interrupt
				mask bit is reset.
21	25	nChip Select	nCS	Input. This active low signal issued by the
				microcontroller selects the COM20020 for
				an access.

TRANSMISSION MEDIA INTERFACE

16,15	19,18	nPulse 2,	nPULSE2,	Output.	In Normal Mode, these active low
		nPulse 1	nPULSE1	signals carry the transmit data information,
				encoded in pulse format, from the
				COM20020 to the media driver circuitry.
				When the device is in Backplane Mode, the
				nPULSE1 signal driver is programmable
				(push/pull or open-drain), while the
				nPULSE2 signal provides a clock with
				frequency of crystal/4.		nPULSE1 is
				connected to a weak internal pull-up resistor
				in backplane mode.
17	20	Receive In	RXIN	Input.	This signal carries the receive data
				information from the line receiver circuitry to
				the COM20020.
18	21	nTransmit	nTXEN	Output.	This signal is used prior to the
		nEnable		Power-upto enable the line drivers for
				transmission. The polarity of the signal is
				programmable by grounding the nPULSE2
				pin.
				nPULSE2 floating before Power-up: nTXEN
				active low (Default option)
				nPULSE2 grounded before Power-up:
				nTXEN active high (This option is only
				available in Backplane Mode)
			MISCELLANEOUS
13,14	16,17	Crystal	XTAL1,	An external crystal should be connected to
		Oscillator	XTAL2	these pins. If an external TTL clock is used
			5