IMP11-A ARPANET interface

The IMP11-A ARPANET interface was a network interface produced by DEC's Computer Special System division for the a UNIBUS, which provided an 1822 interface; the latter could connect to anything that provided a BBN-1822 bit-serial interface, most commonly including IMP interfaces to ARPANET IMPs, but also Packet Radio Network interfaces.

It consists of a BA11-E Mounting Box holding a pair of DR11-B parallel interfaces (the DMA type of DR11 - one for packet input, and one for output), and a custom backplane holding a number of M-series FLIP CHIPs to interface to the IMP, including producing the bit serial input and output. Level converters allow use as either a Local Host or Distant Host interface.

Registers

Register	Abbreviation	Address
Transmit Word Count Register	TXWCR	772410
Transmit Bus Address Register	TXBAR	772412
Transmit Command/Status Register	TXCSR	772414
Transmit Data Buffer Register	TXDBR	772416
Receive Word Count Register	RXWCR	772430
Receive Bus Address Register	RXBAR	772432
Receive Command/Status Register	RXCSR	772434
Receive Data Buffer Register	RXDBR	772436

772410: Transmit Word Count Register (TXWCR)

WC15 <---> WC00
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

772412: Transmit Bus Address Register (TXBAR)

BA15 <---> BA00
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

772414: Transmit Command/Status Register (TXCSR)

ERR	NEX	ATTN	MAINT	Unused			CYCLE	RDY	IE	XBA16-17		Unused	LAST BIT	TX CLR	GO
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

772416: Transmit Data Buffer Register (TXDBR)

Data15 <---> Data00
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

772430: Receive Word Count Register (RXWCR)

WC15 <---> WC00
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

772432: Receive Bus Address Register (RXBAR)

BA15 <---> BA00
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

772434: Receive Command/Status Register (RXCSR)

ERR	NEX	ATTN	MAINT	EOM	IMP NRDY	RDY ERR	CYCLE	RDY	IE	XBA16-17		RX ENBL	HOST RDY	RX CLR	GO
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

772436: Receive Data Buffer Register (RXDBR)

Data15 <---> Data00
15	14	13	12	11	10	09	08	07	06	05	04	03	02	01	00

External links

• IMP11-A PDP-11 Host to IMP Full Duplex NPR Interface