HP E1459A Debounce Clock, Register Port 0 and, Port1/ Port 2 and, Port

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 3-1 shows the allowed values for this register. This register is mirrored at address base + 2Eh. Accessing register base + 1Eh is equivalent to base + 2Eh. Programming the register to 0 is equivalent to programming it to 2, and programming it to 3 is the same as 1.

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	0
Write							No Effect									DEBOUNCE TIME
Read				Always Returns FFFh								0	0	0		DEBOUNCE TIME

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:

Register Value	Bit pattern (hex)	Clock Frequency	Clock Period	Debounce Time
				(4 - 4.5 clock periods)
2 (or 0, default)	0002h	250 kHz	4 μS	16		- 18 μS
3 (or 1)	0003h	125 kHz	8 μS	32		- 36 μS
4	0004h	62.5 kHz	16 μS	64		- 72 μS
5	0005h	31.25 kHz	32 μS	128		- 144 μS
6	0006h	15.63 kHz	64 μS	256		- 288 μS
7	0007h	7.81 kHz	128 μS	512		- 576 μS
8	0008h	3.90 kHz	256 μS	1.0 - 1.13 mS
9	0009h	1.95 kHz	512 μS	2.0 - 2.26 mS
10	000Ah	976 Hz	1 mS	4.1	- 4.6 mS
11	000Bh	488 Hz	2 mS	8.2	- 9.2 mS
12	000Ch	244 Hz	4.1 mS	16.4	- 18.4 mS
13	000Dh	122 Hz	8.2 mS	32.8	- 36.9 mS
14	000Eh	61 Hz	16.4 mS	65.5	- 73.8 mS

HP E1459A Register Definitions 85