Echelon FT 3150 Smart Transceiver - Manual (Page 91)

FT 3120 / FT 3150 Smart Transceiver Data Book 85
Timer/Counter Output Objects
Pulsewidth Output
A timer/counter may 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 may be one of eight values given by Table 3.7.
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 may be one of eight values given by Table 3.8 in
section , Notes. The asserted state of the waveform may 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 3.48.
Figure 3.48 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.
A disabled output is a logic 0 by default unless the invert keyword is used in the I/O object declaration.
Symbol Description
Typ @
10MHz
t
fout
Function call to output update 101 µs
t
ret
Return from function 13 µs
ONE CYCLE
t
ret
NEW OUTPUT
APPEARS ON PIN
HARDWARE
UPDATED
INTERNALLY
START
OF
io_out()
t
fout
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