Browse Prior Art Database

CONCURRENT REMOTE HARDWARE DEBUG USING LOCAL DEBUG CAPABILITIES

IP.com Disclosure Number: IPCOM000014149D
Original Publication Date: 2001-Apr-26
Included in the Prior Art Database: 2003-Jun-19
Document File: 2 page(s) / 46K

Publishing Venue

IBM

Abstract

Disclosed is a solution for allowing access to very low level internal chip information from remote hardware without re-booting the system. This hardware, not normally connected to a dedicated Service Processor (SP), can be connected "on-the-fly". If the remote hardware is identical to that used locally, this method has the additional benefit of allowing reuse of the same debug software. This "on-the-fly" Connection is de-gated to prevent glitching and gated in a way that the Service Processor attached to the System is not aware that the "on-the-fly" connection has been made.

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  CONCURRENT REMOTE HARDWARE DEBUG USING LOCAL DEBUG CAPABILITIES

    Disclosed is a solution for allowing access to very low level internal chip information from remote hardware without re-booting the system. This hardware, not normally connected to a dedicated Service Processor (SP), can be connected "on-the-fly". If the remote hardware is identical to that used locally, this method has the additional benefit of allowing reuse of the same debug software. This "on-the-fly" Connection is de-gated to prevent glitching and gated in a way that the Service Processor attached to the System is not aware that the "on-the-fly" connection has been made.

R em ote A ttached I/O

F unctional I/O D ata P ath

F unctional I/O D ata P ath

C om puter S ystem

"O n-T he-F ly" D ebug P ath

Figure 1: System View

The gating implemented on a system card that is used as both a transmitter and receiver of the IEEE
1149.1 (JTAG) interface is shown in Figure 2. The SP_PRESENT signal is grounded by the SP for local use, but pulled high for remote. Similarly the DEBUG_GND signal is grounded by the debug cable when it is present, but pulled high otherwise. The combination of these two control lines reroutes JTAG when the cable is attached. In this case the chip shown will detach from JTAG when the card is local, and attach to JTAG when remote, without glitching the interface. The existing debug software does not know the reconnection has occurred. In this example the chips are identical, so the supp...