The debounce clock register (base + 1e, Accessing register base + 1e, Is equivalent to base + 2e – HP E1459A User Manual
Page 86
HP E1459A Register Definitions
85
Debounce Clock
Register Port 0 and
Port1/ Port 2 and
Port 3
The Debounce Clock Register (base + 1E
h
) 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 2
N
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 + 2E
h
. Accessing
register base + 1E
h
is equivalent to base + 2E
h
. 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)
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 + 2E
h
.
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 + 2E
h
.
The following table lists the actual values for the debounce times:
b + 1E
h
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
Write
No Effect
DEBOUNCE TIME
Read
Always Returns FFF
h
0
0
0
DEBOUNCE TIME
Register Value
Bit pattern (hex)
Clock Frequency
Clock Period
Debounce Time
(4 - 4.5 clock periods)
2 (or 0, default)
0002
h
250 kHz
4
µ
S
16 - 18
µ
S
3 (or 1)
0003
h
125 kHz
8
µ
S
32 - 36
µ
S
4
0004
h
62.5 kHz
16
µ
S
64 - 72
µ
S
5
0005
h
31.25 kHz
32
µ
S
128 - 144
µ
S
6
0006
h
15.63 kHz
64
µ
S
256 - 288
µ
S
7
0007
h
7.81 kHz
128
µ
S
512 - 576
µ
S
8
0008
h
3.90 kHz
256
µ
S
1.0 - 1.13 mS
9
0009
h
1.95 kHz
512
µ
S
2.0 - 2.26 mS
10
000A
h
976 Hz
1 mS
4.1 - 4.6 mS
11
000B
h
488 Hz
2 mS
8.2 - 9.2 mS
12
000C
h
244 Hz
4.1 mS
16.4 - 18.4 mS
13
000D
h
122 Hz
8.2 mS
32.8 - 36.9 mS
14
000E
h
61 Hz
16.4 mS
65.5 - 73.8 mS
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