Browse Prior Art Database

Read Only Patch Card

IP.com Disclosure Number: IPCOM000082347D
Original Publication Date: 1974-Nov-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 2 page(s) / 65K

Publishing Venue

IBM

Related People

Houdek, ME: AUTHOR

Abstract

The three registers 10, 11 and 12 of Fig. 1 form a part of a processor which includes a read only control store, partitioned into groups identified as ROS 1, ROS 2 and ROS 3. Each of the ROS groups has an addressing capability of 16,384 instructions achieved by a 14-bit wide instruction address 17. A ROS group select register 12 controls which of the three ROS groups is to be addressed during any access time.

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Read Only Patch Card

The three registers 10, 11 and 12 of Fig. 1 form a part of a processor which includes a read only control store, partitioned into groups identified as ROS 1, ROS 2 and ROS 3. Each of the ROS groups has an addressing capability of 16,384 instructions achieved by a 14-bit wide instruction address 17. A ROS group select register 12 controls which of the three ROS groups is to be addressed during any access time.

When it becomes desirable to make changes to the instructions to correct a function deficiency or programming error or to install an additional feature, a ROS patch card 13 can be installed without affecting the modules of the existing ROS groups. ROS patch card 13 replaces base ROS instructions in 32 instruction sections and patches only those sections of the instructions that require change. The organization of the logic allows changes to any 32 instruction section of any of the ROS groups. Up to 64 sections may be changed with one ROS patch card as shown.

The logic diagram of ROS patch card 13 is shown in Fig. 2. Two ROS modules 15 and 16 are connected so that the output of address translator module 15 connects to the input of instruction replacement module 16. The nine high-order bits 21 of the instruction address and the ROS group select lines 18, 19 and 20 provide the input to the address translator ROS module 15. If a section of base ROS instructions to be replaced is being addressed, the read- only storage of address translator m...