
Debounce Clock
Register Port 0 and
Port1/ Port 2 and
Port 3
The Debounce Clock Register (base + 1Eh) can be read or written. This register controls the clock rate to the debouncers. There are only two programmable counters for all four ports. Port 0 and Port 1 share one counter. This counter is controlled when bit 4 of the Control/Status Register is "0". Port 2 and Port 3 share the other counter and are accessed when bit 4 of the Control/Status Register is "1". A 2N counter is used to generate the clock, so times are binary powers. Table
Debounce Clock Register Port 0 and Port 1/Port 2 and Port 3 (base + 1Eh)
b + 1Eh | 15 | 14 | 13 |
| 12 | 11 |
| 10 | 9 | 8 | 7 | 6 | 5 | 4 | 3 |
| 2 | 1 |
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Write |
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| No Effect |
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| DEBOUNCE TIME |
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Read |
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| Always Returns FFFh |
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| 0 | 0 | 0 |
| DEBOUNCE TIME |
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When BS = 0 in the Status/Control Register, the debounce clock for Port 0 and Port 1 are accessed. Port 0 and Port 1 use the same debounce clock. With BS = 0 any value programmed into or read from this register will be the same as the register at b + 2Eh.
When BS = 1 in the Status/Control Register, the debounce clock for Port 2 and Port 3 are accessed. Port 2 and Port 3 use the same debounce clock. With BS = 1 any value programmed into or read from this register will be the same as the register at b + 2Eh.
The following table lists the actual values for the debounce times:
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| Register Value | Bit pattern (hex) | Clock Frequency | Clock Period | Debounce Time |
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| (4 - 4.5 clock periods) |
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| 2 (or 0, default) | 0002h | 250 kHz | 4 μS | 16 | - 18 μS |
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| 3 (or 1) | 0003h | 125 kHz | 8 μS | 32 | - 36 μS |
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| 4 | 0004h | 62.5 kHz | 16 μS | 64 | - 72 μS |
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| 5 | 0005h | 31.25 kHz | 32 μS | 128 | - 144 μS |
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| 6 | 0006h | 15.63 kHz | 64 μS | 256 | - 288 μS |
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| 7 | 0007h | 7.81 kHz | 128 μS | 512 | - 576 μS |
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| 8 | 0008h | 3.90 kHz | 256 μS | 1.0 - 1.13 mS |
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| 9 | 0009h | 1.95 kHz | 512 μS | 2.0 - 2.26 mS |
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| 10 | 000Ah | 976 Hz | 1 mS | 4.1 | - 4.6 mS |
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| 11 | 000Bh | 488 Hz | 2 mS | 8.2 | - 9.2 mS |
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| 12 | 000Ch | 244 Hz | 4.1 mS | 16.4 | - 18.4 mS |
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| 13 | 000Dh | 122 Hz | 8.2 mS | 32.8 | - 36.9 mS |
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| 14 | 000Eh | 61 Hz | 16.4 mS | 65.5 | - 73.8 mS |
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HP E1459A Register Definitions 85