Browse Prior Art Database

High-Speed Micro Channel Arbitration Via Selection of Arbitration Levels

IP.com Disclosure Number: IPCOM000120336D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 2 page(s) / 56K

Publishing Venue

IBM

Related People

Arimilli, RK: AUTHOR [+3]

Abstract

Disclosed is a method for decreasing the time required for parallel arbitration. This can be specifically applied to the Micro Channel*.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 57% of the total text.

High-Speed Micro Channel Arbitration Via Selection of Arbitration
Levels

      Disclosed is a method for decreasing the time required
for parallel arbitration.  This can be specifically applied to the
Micro Channel*.

      The arbitration mechanism on the Micro Channel requires bus
con- tenders to arbitrate in parallel on a 4-bit do-OR/open-collector
bus.  (Each contender contains a 4-bit programmable arbitration
level.)  The parallel arbitration allows each bus contender a maximum
of 50 ns to drive or to release the next least significant ARB bit
based on the state of the current ARB bit.  Empirically, the maximum
arbitration cycle on the Micro Channel is 290 ns, 140 ns due to two
RC restores plus 150 ns for response from the contender's logic.
Addition of potential skews of 20 to 30 ns from the Central
Arbitration Control Point may bring the worst case to 320 ns.  The
arbitration time must be programmmed to be 400 ns to accommodate
this.

      By analyzing the RC restore cases, however, a subset of
arbitration levels can be obtained to limit the number of RC
restores.  If the 10XX levels are disallowed, then the maximum number
of RC restores on the ARB lines is one, making the maximum
arbitration time 250 ns (150 ns + 70 ns + skew), and allowing the
programmable arbitration time to be set to 300 ns instead of 400 ns.

      In general for an n-bit ARB bus:
        ------- n -------
        10XX XXXX .. XXXX        Disallowing t...