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Test of the Wrap Value of a TIMER Disclosure Number: IPCOM000038331D
Original Publication Date: 1987-Jan-01
Included in the Prior Art Database: 2005-Jan-31

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Picon, JL Pin, C [+details]


This invention is to be used in a machine comprising timers working in two resolution modes: high resolution mode and low resolution mode and having long wraparound times which have to be checked at the machine initialization. The circuit shown in the drawing allows the checking time to be reduced in a significant way. As shown in Fig. 1, the timer comprises a three-byte counter which can be used in two resolution modes: high resolution if its 23 high- order bits are used and low resolution if the resolution divider (11 bits) is used. The wraparound of this timer occurs when the hexadecimal value "666666" is decoded on the 23 high-order bits. This occurs after 524 milliseconds in high resolution mode and after 35.8 minutes in low resolution mode, assuming that the C and B clocks are working at 125 microseconds.