DS2480 Datasheet, PDF (15/26 Pages) Dallas Semiconductor – Serial 1.Wire Line Driver

DS2480
PULSE WAVE FORMS, DISARMED
The pulse command can be used to generate a strong
pull–up to 5V and a 12V programming pulse, respec-
tively. The duration of the pulse is predefined if the
parameter value code of parameter 010 (Programming
Pulse Duration) and parameter 011 (Strong Pull–Up
Duration), has a value from 000 to 110 (see Table 4).
Figures 7a and 7b show the timing of a pulse with prede-
fined duration, which should be considered the normal
case. If an infinite duration is chosen (parameter value
code 111), the host must terminate the pulse command,
as shown in Figures 7c and 7d. All versions of Figure 7
assume that bit 1 of the pulse command is 0, i.e., dis-
armed mode. See section Communication Commands,
Pulse, for more details on possibilities of the pulse
command.
STRONG PULL–UP TO 5V, PREDEFINED DURATION Figure 7a
END OF PREVIOUS
5V
TIME SLOT
IDLE
TIME
t_SPU
IDLE
TIME
BEGIN OF NEXT
TIME SLOT
0V
t₁
t₂
The processing of a pulse command is essentially the
same, regardless if a strong pull–up or a programming
pulse is requested. At t₁ the host starts sending the
pulse command byte. At t₂ the DS2480 has received the
command and immediately generates the pulse. The
pulse ends at t₃ and the DS2480 sends out the com-
mand response byte to inform the host that the com-
t₃
t₄
mand is completed. The idle time between t₁ and t₂ is
determined by the time to transmit the command byte at
the selected baud rate. The idle time between t₃ and t₄ is
comprised of the time to transmit the response byte,
plus the response time of the host plus the time to trans-
mit the command and/or data to generate the next time
slot.
12V PROGRAMMING PULSE, PREDEFINED DURATION Figure 7b
12V
END OF PREVIOUS
5V
TIME SLOT
IDLE
TIME
STEEP SLOPES
t_PP
IDLE
TIME
BEGIN OF NEXT
TIME SLOT
0V
t₁
t₂
A correct programming pulse can only be generated if
the 12V programming voltage is available at the Vpp pin
of the DS2480. The slew rate of the rising and falling
edge of the programming pulse (“steep slopes”) is not
actively controlled by DS2480.
t₃
t₄
For EPROM programming, only a single slave device
should be connected to the 1–Wire bus and the cable
must to be short, not to exceed a few meters. One
should not attempt generating a programming pulse
with a non–EPROM device on the bus; this may dam-
age the device as well as the DS2480.
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