DS2480B Maxim Integrated Products, DS2480B Datasheet - Page 21

• Manufacturer Part Number: DS2480B
• Description: IC LINE DRVR W/SENSOR 1-W 8-SOIC
• Manufacturer: Maxim Integrated Products
• Type: Line Driver, Transmitterr

Specifications of DS2480B

• Number Of Drivers/receivers: 1/0
• Protocol: RS232
• Voltage - Supply: 4.5 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

DS2480B
SINGLE BIT WITH STRONG PULLUP
Similar to the Pulse command, the Single Bit command also allows generating a strong pullup
immediately following a time slot. The strong pullup of the Single Bit command, however, is controlled
directly by bit 1 of the command code and therefore needs not be armed. Since the DS2480B remains in
Command Mode when using the Single Bit command, any duration of the strong pullup including
dynamic as well as infinite may be selected.
Strong pullup immediately following a single time slot is used in conjunction with the crypto iButton.
Under certain conditions the crypto iButton sends out a single bit and then immediately starts executing a
firmware program. This raises the energy demand significantly until the program comes to a halt, at
which point the host computer has to be interrupted. The dynamic duration option of the strong pullup
supplies energy for any duration as needed and automatically notifies the host that the crypto iButton is
ready for the next command.
Figure 9a. SINGLE BIT WITH STRONG PULLUP, PREDEFINED DURATION
Figure 9 shows the timing of the Single Bit command immediately following strong pullup. For
predefined and dynamic duration (Figure 9a) the timing is as follows: At t
the time slot is completed.
1
Now the DS2480B activates the strong pullup and simultaneously starts sending the response byte of the
Single Bit command to the host. At t
the strong pullup ends and the DS2480B sends out a pulse response
2
byte. The idle time between t
and t
is comprised of the time to transmit the pulse response byte, plus the
2
3
response time of the host plus the time to transmit the command and/or data to generate the next time slot.
Figure 9b. SINGLE BIT WITH STRONG PULLUP, INFINITE DURATION
For infinite duration (Figure 9b) the strong pullup also begins immediately after the time slot is
completed. To end the strong pullup, the DS2480B must receive a Termination command, code F1h,
which occurs at t
. The termination command does not generate a response byte. The DS2480B will then
2
immediately end the strong pullup and send out a pulse response byte. Everything else is the same as with
predefined duration.
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