Original Publication Date: 1971-Jan-01
Included in the Prior Art Database: 2005-Feb-22
Grant, CH: AUTHOR [+4]
In a multiplexor channel which contains 64 subchannels, the subchannels may be either all unshared, all shared or a mixture of both types.
In a multiplexor channel which contains 64 subchannels, the subchannels may be either all unshared, all shared or a mixture of both types. The combinations of shared and unshared subchannels may take the following form: Unshared Subchannels Shared Subchannels
64 (64 Device Addresses) 0
56 (56 Device Addresses) 1 (200 Device Addresses)
48 (48 Device Addresses) 2 (208 Device Addresses)
40 (40 Device Addresses) 3 (216 Device Addresses)
32 (32 Device Addresses) 4 (224 Device Addresses)
24 (24 Device Addresses) 5 (232 Device Addresses)
16 (16 Device Addresses) 6 (240 Device Addresses)
8 ( 8 Device Addresses) 7 (248 Device Addresses)
0 8 (256 Device Addresses).
To sustain operations on the subchannels, the channel provides a Unit Control Word Storage (UCWS) to buffer control information. Each subchannel has associated with it an area of the UCWS designated as the Unit Control Word (UCW) area. There are two UCW formats, one for unshared subchannels consisting of two words and one for shared subchannels consisting of sixteen words two of which have a format identical to the two word UCW of the unshared subchannel, a third word retaining the unit address of the device which is currently using the shared subchannel, and thirteen unused words. Thus, the UCWS can at one extreme consist of eight groups of 8=64 UCW's for a configuration of all unshared subchannels and at the other extreme eight groups of 1=8 UCW's for a configuration of all shared subchannels.
A flexible assignment of device addresses is provided with the determination of whether a device is shared or unshared being address independent. Using plug cards, unshared subchannels are plugged in groups of eight contiguous addresses, shared subchannels are plugged in groups of sixteen contiguous addresses with a maximum of eight groups being plugged at any one time. The UCW address in the UCWS is formed directly from the device address. The UCW address bits 0 and 1 are decoded to one of four lines and bits 2, 3 and 4 to one of eight lines. If the address is a valid address, the decoded outputs will be plugged to one of a group of eight AND circuits representing an unshared subchannel or to one of a group of eight AND circuits representing a shared subchannel in accordance with the chosen address assignments, the corresponding AND circuit from the unselected group being degated. Thus, eight AND circuits will be effective and eight corresponding AND circuits will be degated. In the example shown, two AND circuits associated with the shared subchannels and six AND circuits associated with the unshared subchannels are plugged to the decoders. The output of the selected AND circuit is passed via an OR circuit and encoded to form a three-bit Y address which is applied to bits 1, 2 an...