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TI486 Microprocessor - Al Kossow's Bitsavers

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Functional Timing<br />

The <strong>TI486</strong>SLC/E samples the FLUSH input on the rising edge of CLK2<br />

corresponding to the beginning of phase 2 of the internal processor clock. If<br />

FLUSH is asserted, the <strong>TI486</strong>SLC/E invalidates the entire contents of the<br />

internal cache. The actual point in time where the cache is invalidated depends<br />

upon the internal state of the execution pipeline. FLUSH must be asserted for<br />

at least two CLK2 periods and must meet specified setup and hold times to be<br />

recognized on a specific CLK2 edge.<br />

3.2.7 Address Bit 20 Masking<br />

The <strong>TI486</strong>SLC/E can be forced to provide 8086 1-MByte address wraparound<br />

compatibility by setting the A20 bit in the CCRO configuration register and<br />

asserting the A20M input. When the A20M is asserted, the 20th bit in the<br />

address to both the internal cache and the external bus pin is masked (zeroed).<br />

3-36<br />

<strong>TI486</strong>SLCIE Bus Interface

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