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Method to Utilize Rom-Based Power-On-Self-Test Code in Manufacturing Test

IP.com Disclosure Number: IPCOM000061552D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 15K

Publishing Venue

IBM

Related People

Day, MN: AUTHOR [+4]

Abstract

A method is described which uses the extensive Power-On-Self-Test (POST) code in the system Read-Only Memory (ROM) of a Personal Computer (PC) for manufacturing test of the system board in a functional tester and burn-in chamber that has no system memory or I/O devices installed on the system board under test. In most production manufacturing lines there is a functional test and burn-in of the electronic devices being manufactured. Historically, on the PC product lines this has been performed by the system ROM on the system board handing control to special manufacturing test routines loaded into main memory by the tester. The PCjr system made some use of the Power-On-Self-Test code built into the system ROM for functional test but not for board burn-in.

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Method to Utilize Rom-Based Power-On-Self-Test Code in Manufacturing Test

A method is described which uses the extensive Power-On-Self-Test (POST) code in the system Read-Only Memory (ROM) of a Personal Computer (PC) for manufacturing test of the system board in a functional tester and burn-in chamber that has no system memory or I/O devices installed on the system board under test. In most production manufacturing lines there is a functional test and burn-in of the electronic devices being manufactured. Historically, on the PC product lines this has been performed by the system ROM on the system board handing control to special manufacturing test routines loaded into main memory by the tester. The PCjr system made some use of the Power-On-Self-Test code built into the system ROM for functional test but not for board burn-in. Normally the systems under test that are executing the ROM code for manufacturing test have had main memory installed in order to run the test. On the new product system board the system ROM contained a very extensive POST. This was provided since the product is to be used in a portable environment where the user may not have all the manuals and diagnostic diskettes needed to test the system. A method was therefore needed to be able to utilize all of the code in the ROM to test the system board during the manufacturing process and at elevated temperatures. This invention discloses this method for the new product system board without main memory installed. This method includes microcode and a special hardware feature designed into the system. The POST code uses main memory beginning at address 0 and, since main memory is separate from the board, what memory there is on the board had to be used. The system board contains a 16K refresh buffer at address B0000H used by the video display. The hardware has designed into it a memory substitution register. With a port write to this register, addresses to the 16K memory at address 0 are decoded to address memory at B0000H. The POST is able to execute with or without main memory installed. The microcode (POST) is designed to provide the following: 1. A means of determining if the machine is in manufacturing test and subsequently set memory substitution, with 100% certainty memory substitution would not happen in the user environment. 2. A means of communicating to manufacturing any failures and signalling a successful POST. 3. A way for manufacturing to signal POST to restart without having to power off and on the board. 4. The capability to load additional test software into memory for execution without any input devices. The latter three requirements are met by utilizing the I/O bus connector. It is designed with three ports and a printer interface which includes a transmit out line and printer status lines. The ports provide parallel data transfer, and the printer lines provide status and control signalling. An explanation of POST's novel use of this connector to al...