DS2480B Datasheet DS2480B | P19-P21

DS2480B

19 of 31

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 damage the device as well as the DS2480B.

Certain applications may require a duration for a strong pullup or programming pulse that cannot be

realized using one of the predefined values. Selecting infinite duration allows the host to generate pulses

of any length. As a consequence, however, the host becomes responsible to actively control the duration

of the pulse. Failing to do so may require a power-on reset or master reset cycle of the DS2480B. For this

reason, infinite duration should only be used if absolutely necessary.

The time to end a pulse of infinite duration strongly depends on the baud rate of the communication

between host and DS2480B. Neglecting the response time of the host, the minimum pulse durations are:

86.8µs at 115.2kbps, 173.6µs at 57.6kbps, 520µs at 19.2kbps, and 1.04ms at 9.6kbps.

Figure 7c. STRONG PULLUP TO 5V, INFINITE DURATION

As before, processing the command is essentially the same, regardless if it is for a strong pullup or a

programming pulse. At t

the host starts sending the Pulse command byte. At t

the DS2480B has

received the command and immediately activates the strong pullup or switches in the 12V programming

voltage. To end the pulse, the DS2480B must receive a Termination command, code F1h, which occurs at

. The Termination command does not generate a response byte. The DS2480B will immediately end the

pulse and send out the response byte of the pulse command. The idle time between t

and t

is determined

by the time to transmit the command byte at the selected baud rate. The idle time between t

and t

comprised of the time to transmit the pulse response byte, plus the response time of the host plus the time

to transmit the command and/or data to generate the next time slot.

Figure 7d. 12V PROGRAMMING PULSE, INFINITE DURATION

DS2480B

20 of 31

PULSE WAVEFORM, ARMED

As explained in the Communication Commands section, bit 1 of the Pulse command allows the arming of

a strong pullup to 5V if the bit is set to 1. If the strong pullup is armed and the device is switched to Data

Mode, there will be a strong pullup immediately following every byte on the 1-Wire bus. This mode is

implemented to provide extra energy when writing to EEPROM devices or to do a temperature

conversion with the DS1920 temperature i

Button, for example. These devices need a strong pullup

immediately after the power-consuming activity has been initiated by a command code.

To arm the strong pullup, one usually generates a “dummy” pulse with bit 1 being 1 while the device is in

Command Mode. To save time, the dummy pulse may immediately be terminated by sending the

Termination command, code F1h. Then one switches to Data Mode and sends a command code that

makes one or more slaves on the 1-Wire bus require extra energy. After the command execution is

finished, one switches back to Command Mode and disarms the strong pullup by generating another

dummy pulse. A complete temperature conversion sequence that shows the use of the armed pulse is

included in the Software Driver Examples section .

Figure 8. STRONG PULLUP TO 5V, ARMED, PREDEFINED DURATION

Figures 8 shows the timing of the strong pullup in Data Mode. At t

the 8

time slot of the byte sent to the

1-Wire bus is completed. Without any delay the DS2480B now activates the strong pullup and

simultaneously starts sending the data response byte to the host. At t

the strong pullup ends and the

DS2480B sends a pulse response byte to the host. The idle time between t

and t

is comprised of the time

to transmit the pulse response byte, plus the response time of the host plus the time to transmit the

command and/or data to generate the next time slot. Since in Data Mode the Pulse Termination command

is not applicable, the duration of the strong pullup must be limited. See Table 4, parameter 011 (Strong

Pullup Duration) for details.

Dynamic duration is permissible in conjunction with the armed pulse function. However, the load sensor

does not have the sensitivity required for detecting when the high current demand of a single 1-Wire

temperature sensor or EEPROM device ends. Since the duration of the high current demand of such

devices depends on temperature and is slightly different for every individual device, even with multiple

EEPROMs or temperature sensors operating simultaneously, dynamic duration should not be used.

Infinite duration, if accidentally selected, will require a power-on or master reset cycle to get the

DS2480B back to communicating with the host.

DS2480B

21 of 31

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 i

Button 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 i

Button 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.

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

byte. The idle time between t

and t

is comprised of the time to transmit the pulse response byte, plus the

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

immediately end the strong pullup and send out a pulse response byte. Everything else is the same as with

predefined duration.

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P21 P22-P24 P25-P27 P28-P30 P31-P31

DS2480B

Mfr. #:

Buy DS2480B

Manufacturer:

Maxim Integrated

Description:

Buffers & Line Drivers

Lifecycle:

New from this manufacturer.

Delivery:

DHL FedEx Ups TNT EMS

Payment:

T/T Paypal Visa MoneyGram Western Union

Products related to this Datasheet

DS2480B