blog:286_shootout_vlsi_vl82c311l

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blog:286_shootout_vlsi_vl82c311l [2021/03/14 12:34] – [Repairs] johnblog:286_shootout_vlsi_vl82c311l [2021/04/23 14:09] (current) – [Further Testing] john
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 The held reset light now goes out, and the CLK light stays lit. So that's an improvement. Still no error codes though. The held reset light now goes out, and the CLK light stays lit. So that's an improvement. Still no error codes though.
 +
 +==== Further Testing ====
 +
 +=== Clock Signals ===
 +
 +The 14MHz oscillator which was still fitted to the board on receiving it is working; the clock is present on the output pin from the can as well as on ISA socket pin B30 (//OSC//):
 +
 +{{:blog:286:20210423_133918.png?600|}}
 +
 +There is an 8MHz clock present on ISA socket pin B20 (//CLK//):
 +
 +{{:blog:286:20210423_134011.png?600|}}
 +
 +Processor pin 31 (//CLK//) has a 9.996MHz clock:
 +
 +{{:blog:286:20210423_135456.png?600|}}
 +
 +//This doesn't seem correct//. The processor is a 20MHz unit, and is being driven, as is normal on a 286, by a standard DIL can oscillator of 2x the processor frequency (i.e. 40MHz). The definition for pin 31 is that it //"is divided by 2 internally within the processor to generate the processor clock"// (from the {{ :blog:286:amd_80286_datasheet_june_1989_.pdf|AMD 80286 datasheet}})... that would mean the processor is only at 5MHz. Unless I misunderstand the datasheet, something is drastically wrong here.
 ===== Configuration ===== ===== Configuration =====
  
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  • Last modified: 2021/03/14 12:34
  • by john