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Address Determination for Last Byte of a VFL Word

IP.com Disclosure Number: IPCOM000092555D
Original Publication Date: 1966-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Adler, JG: AUTHOR [+2]

Abstract

In data processing systems operating on variable length operands, it is necessary to determine when the last byte of the operand is being processed. In this processor, the VFL words are processed one byte per cycle. A maximum of eight bytes is stored in buffer register 1 and sequentially gated out under control of byte address counter BC 4 through gates 2 to bus 3 for processing. VFL processor 5 performs the required modification on the input byte and sends the resulting byte over bus 6 to storage, either a main store or a temporary buffer storage.

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Address Determination for Last Byte of a VFL Word

In data processing systems operating on variable length operands, it is necessary to determine when the last byte of the operand is being processed. In this processor, the VFL words are processed one byte per cycle. A maximum of eight bytes is stored in buffer register 1 and sequentially gated out under control of byte address counter BC 4 through gates 2 to bus 3 for processing. VFL processor 5 performs the required modification on the input byte and sends the resulting byte over bus 6 to storage, either a main store or a temporary buffer storage.

VFL operand processing is performed under control of instructions held in OP stack 14. The instructions are received from the processors instruction unit I Box, not shown, and stored sequentially in stack 14. There is one instruction for each word transferred to register 1. The instruction operates through processor controls 7 to control the gating of data. Since the I Box controls the fetching of the VFL operands in eight-byte words, it can determine which instruction is for the last byte of the operand and it indicates this instruction by setting a last instruction bit 8 with the instruction in stack 14. Since, however, the I Box predecodes instructions, it is not available by the time the last instruction is being processed. The determination of when the last byte of the operand is being processed is left to the execution unit.

The I Box on the first instruction of t...