Rabbit BL2600, Руководство пользователя

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20 SBC BL2600
The use of these channels for interrupts, input capture, and as quadrature decoders is described
in the
Rabbit 3000 Microprocessor User’s Manual , and is illustrated through sample pro-
grams in the Dynamic C
SAMPLES\RABBIT3000
folder. Table 5 lists these alternate uses.
3.2.2 PWM Outputs
Digital inputs DIN20–DIN23 can be used as PWM output channels by setting the jumper
on header JP4 across pins 7–8 to pull the digital inputs to ground. Once the PWM driver
sets up a given PWM channel, the corresponding digital input channel is no longer avail-
able for use as a digital input. The output voltage swing will be 0 to 1.65 V, which is not
suitable for interfacing only to CMOS-level inputs. Since the output impedance is approx-
imately 13 k

, the input impedance of the circuit the PWM output is connected to should
be at least 10 times as high.
The sample program
PWM.C
in the
IO
subdirectory in
SAMPLES\BL2600
shows how to
set up and use the PWM outputs.
The actual switching threshold is approximately
1.40 V. Anything below this value is a logic 0, and
anything above is a logic 1
.
The digital inputs are
each fully protected over a range of -36 V to +36 V,
and can handle short spikes of ±40 V.
NOTE: If the inputs are pulled up to +K or to
DCIN, the voltage range over which
the digital inputs are protected changes
to +K (or DCIN) – 36 V to +36 V.
Individual DIN16–DIN23 channels may be used
for interrupts, input capture, as quadrature decod-
ers, or as PWM outputs.
Figure 8. BL2600 Digital Input
Protected Range
Table 5. Alternate Uses for BL2600 Channels DIN16–DIN23
Channel Interrupt Input Capture
Quadrature
Decoder
PWM Outputs
DIN16 ×
DIN17 ×
DIN18 ×
DIN19 × ×
DIN20 × ×
DIN21 × × ×
DIN22 × ×
DIN23 × × ×
+40 V
+36 V
+3.3 V
–40 V
Normal Switching
Levels
Spikes
Digital Input V
oltage
Spikes
Spikes