Browse Prior Art Database

Fast Addressing Logic to Improve Read Access Time From a Register File

IP.com Disclosure Number: IPCOM000120641D
Original Publication Date: 1991-May-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 62K

Publishing Venue

IBM

Related People

Arimilli, RK: AUTHOR [+3]

Abstract

Disclosed is a circuit to improve read access from a register file (array) to meet Micro Channel* Bus Master read timings.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 67% of the total text.

Fast Addressing Logic to Improve Read Access Time From a Register File

      Disclosed is a circuit to improve read access from a
register file (array) to meet Micro Channel* Bus Master read timings.

      During Bus Master DMA operations on the Micro Channel, the I/O
Channel Controller (IOCC) acts as a slave for transfers to and from
system memory.  DMA data is stored in two register files, each 4
bytes wide and 128 lines long. These two register files are
concatenated to form an organization 8 bytes wide and 128 lines long,
totalling 1024 bytes.  These bytes are addressed using 10 bits -
ADDR(0-9). Fig. 1 shows a way to implement the addressing logic to
the register file.  ADDR(0-6) are used to address one of the 128
lines.  DMA read data from register files A and B are at the input of
MUX D.  ADDR(7) selects data from register file A or B.  When the Bus
Master is reading register file A, ADDR(7)=0, data from register file
B has been accessed and is available at the output of MUX D by
switching its control (ADDR(7)).  But if the Bus Master register file
B and switches to register file A sequentially, another access of
register file A is required because the line address has changed.
This delay is too large to meet the Micro Channel timings for read
data.

      Fig. 2 represents an implementation that hides the read access
time.  The line address for register files A and B are separate.
Register file B is addressed using ADDR(0-6). Register file A can...