AN2028 MC68SC302 - Datasheet Archive
Order by: AN2028 MC68SC302 Design Advisory #1 MC68SC302 Passive ISDN Protocol Engine Freescale Semiconductor, Inc. March 31, 1997
Freescale Semiconductor Order by: AN2028 AN2028 MC68SC302 MC68SC302 Design Advisory #1 MC68SC302 MC68SC302 Passive ISDN Protocol Engine Freescale Semiconductor, Inc. March 31, 1997 This purpose of this note is to make designers of MC68SC302 MC68SC302 based ISA PNP products aware of a problem with the Award Plug and Play BIOS that affects the MC68SC302 MC68SC302. The Award BIOS Plug and Play Initialization routine does not write to the Interrupt Request Type Select 0 register (address 71) when the Plug and Play resource data is requesting a high edge sensitive interrupt as required by the Plug and Play ISA Specification 1.0a. The MC68SC302 MC68SC302 Interrupt Request Type Select 0 has a default of low edge after reset. Since the Award BIOS never programs this register during its Plug and Play initialization sequence the MC68SC302 MC68SC302 will issue interrupts low edge sensitive and not be recognized in high edge sensitive systems. This is only a problem with the following conditions: a non-Windows 95 system such as Windows NT (current versions without Plug and Play) or Windows 3.1, AND motherboards using the Award BIOS with this incompatibility. Windows 95 does not have this problem and will rerun the Plug and Play initialization sequence correctly. No other BIOSes have been found to have this bug. The workaround is to write to the Interrupt Request Type Select 0 register with a $02 which will set the MC68SC302 MC68SC302 IRQ to a high, edge sensitive state. This can be done when the MC68SC302 MC68SC302 device driver is invoked. This is an acceptable workaround for Windows NT systems. Since most PC motherboards use high edge sensitive interrupt logic, a future revision of the MC68SC302 MC68SC302 is planned to default after reset to high edge sensitive interrupts to improve its compatibility with non-compliant Plug and Play initialization routines. It is still advised to implement the work around described above if your product could be required to operate a non-compliant system. Information in this document is provided solely to enable system and software implementers to use Freescale Semiconductor products. There are no express or implied copyright licenses granted hereunder to design or fabricate any integrated circuits or integrated circuits based on the information in this document. Freescale Semiconductor reserves the right to make changes without further notice to any products herein. Freescale Semiconductor makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does Freescale Semiconductor assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation consequential or incidental damages. "Typical" parameters which may be provided in Freescale Semiconductor data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including "Typicals" must be validated for each customer application by customer's technical experts. Freescale Semiconductor does not convey any license under its patent rights nor the rights of others. Freescale Semiconductor products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the Freescale Semiconductor product could create a situation where personal injury or death may occur. Should Buyer purchase or use Freescale Semiconductor products for any such unintended or unauthorized application, Buyer shall indemnify and hold Freescale Semiconductor and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that Freescale Semiconductor was negligent regarding the design or manufacture of the part. © Freescale Semiconductor, Inc., 2004. All rights reserved.