Browse Prior Art Database

Untested Code Path Detector

IP.com Disclosure Number: IPCOM000120350D
Original Publication Date: 1991-Apr-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 3 page(s) / 109K

Publishing Venue

IBM

Related People

Millas, RJ: AUTHOR [+4]

Abstract

This article describes a circuit arrangement which is used to detect untested microcode in a processor by recording accesses made to instruction memory.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Untested Code Path Detector

      This article describes a circuit arrangement which is
used to detect untested microcode in a processor by recording
accesses made to instruction memory.

      A hardware device known as an untested code path detector
(UCPD) is disclosed herein which detects untested microcode by
recording accesses made to instruction memory. In this design, two
digital signal processor (DSPs) (not shown) share a common
instruction memory.  Figs.  1 and 2 show the circuit used for this
DSP system.  This circuit detects and records accesses made to each
instruction memory location by either DSP (not shown).

      A Motorola 68000 (68K)-based controller card which is used to
control the DSP based card, is also used to control the UCPD.  Upon
initialization of the UCPD, the 68K clears the UCPD's random-access
memory (RAM).  Once the DSP instruction RAM is loaded and the DSPs
enabled, the DSPs start executing and the code path detection process
begins. After running the test cases, the DSPs are reset and the
UCPD's RAM is read by the 68K.  Table 1 shows how the data in each
location is interpreted.

      Table 1.  Interpretation of UCPD Data.
HDB = Host Data Bus (68K data bus)
HDB 0 - 12     HDB 14    HDB 15         Meaning
       0           0         0      Location not executed by
                                    either DSP
       0           0         1      Location executed by DSP2
       0           1         0      Location executed by DSP1
       0           1         1      Location executed by both
                                    DSPs

      During execution, 74F257 multiplexers are directed so that the
address of the instruction being fetched is also used by the UCPD
RAM.  A one is written to the selected UCPD RAM location to indicate
that the...