29 lines
1.4 KiB
Plaintext
29 lines
1.4 KiB
Plaintext
AST RESEARCH TECHNICAL BULLETIN TB-0143 1-15-86
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TWO SIXPAKPLUS CLOCK CHIPS
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Recently, the clock chip on the SixPakPlus has been changed to a
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different vendor. The latest version of the SixPakPlus utilizes
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a Ricoh RP5C15, as opposed to the earlier versions of the
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SixPakPlus using a National Semiconductor part number MM58167.
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Since this change has taken place, the question has been raised
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as to how the ASTCLOCK.COM program (included with SuperPak
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Version 4.3) can tell the difference between these two chips.
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Internal address "D" is used by ASTCLOCK to determine which chip
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is being used. The address was chosen for the following reasons.
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For the Ricoh clock chip, this address is a "read-only" address;
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it ALWAYS returns a "0" when read. The same address for the
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National Semicoductor chip is RAM and will read back whatever is
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written to it.
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So ASTCLOCK writes a "1" to address D, bit one. If the result is
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a "0", the program knows a Ricoh chip is present and goes to the
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appropriate place within the program to read this chip.
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Conversely, if a "1" is read back by ASTCLCOK, then the program
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knows to use the portion of the clock dedicated to the National
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Semiconductor chip.
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