Coupling unit designed for bidirectional data transfer between a CII 90-80 or CII 90-40 computer and a CII 90-10 computer

The present paper describes a coupling unit designed for bidirectional data transfer between a CII 90-80 or CII 90-40 computer and a CII 90-10 computer. Data transfer is processed from the parallel path programmed system [POT/BPO, PIN/BPI] of these computers. Data transfers are block data transfer using the INPUT/OUTPUT transfer by block instruction[BPI/BPO]of the CII 90-10 computer and the INPUT /OUTPUT transfer instruction of the CII 90-80 or 90-40 computer in the repeat mode[REP (PIN/POT).] This coupling unit performs: 1 - The initial calling-sequence between the two computer, i.e.: the interrupt request of the receiving computer and the routing of data transfer parameters. 2 - The synchronisation of the request and response exchanged by the two computer in elementary word data transfer. 3 - 12 bits words in 24 bits words assembling for the way of transfer from the 90-10 to the 90-80, - 24 bits words in 12 bits words disassembling for the way of transfer from the 90-80 to the 90-10. The coupling unit allows: 1- The freedom for each computer to call and set the transmission for his own. 2 - The transfer of data blocks of indifferent size: between 1 and 4096 12 bits words for the way 90-10→90-80 - between 1 and 2048 24 bits words for the way 90-80→90-10. It does not need additional optional device to interface with the 90-10 computer [24 bits parallel extension not needed] It increases the rate of transfer compared to the use of this option in a factor of 6. The coupling unit works at the maximum possible speed permitted by the path system used for the coupling of these two computers: a 24 bits word is transferred in both ways each 3 or 4 computer cycles, that is to say each 5,25 or 7 microseconds. (authors)