Specifications

PL 3120/PL 3150/ PL 3170 Power Line Smart Transceiver Data Book 99
Pulsewidth Output
A timer/counter can be configured to generate a pulsewidth modulated repeating waveform. In pulsewidth short
function, the duty cycle ranges from 0% to 100% (0/256 to 255/256) of a cycle in steps of about 0.4% (1/256). The
frequency of the waveform can be one of eight values given by Table 3.9.
In pulsewidth long function, the duty cycle ranges from 0% to almost 100% (0/65,536 to 65,535/65,536) of a cycle in
steps of 15.25 ppm (1/65,536). The frequency of the waveform can be one of eight values given by Table 3.10 in the
Notes section at the end of this chapter. The asserted state of the waveform can be either logic high or logic low. Writing
a new pulsewidth value to the device takes effect at the end of the current cycle. A pulsewidth modulated signal
provides a simple means of digital-to-analog conversion (see Figure 3.54).
ONE CYCLE
NEW OUTPUT
APPEARS ON PIN
HARDWARE
UPDATED
INTERNALLY
START
OF
io_out()
ONE CYCLE
TIME
PULSEWIDTH
OUTPUT
System Clock
Divide Chain
Timer/Counter 1
Timer/Counter 2
IO10
IO9
IO8
IO0
IO1
IO2
IO3
IO4
IO5
IO6
IO7
High Current Sink Drivers
IO11
t
fout
t
ret
Symbol Description
Typ @
10MHz
t
fout
Function call to output update 101 µs
t
ret
Return from function 13 µs
Figure 3.54 Pulsewidth Output Latency Values
The new output value will not take effect until the end of the current cycle. There are two exceptions to this rule. If the
output is disabled, the new (non-zero) output will start immediately after t
fout
. Also, for a new output value of zero,
the output is disabled immediately and not at the end of the current cycle.