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