DS75LV Просмотр технического описания (PDF) - Maxim Integrated

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DS75LV

Digital Thermometer and Thermostat

Maxim Integrated 

DS75LV

Digital Thermometer and Thermostat

Software POR: The soft power-on reset (POR) com-

mand is 54h. The master sends a START followed by an

address byte containing the DS75LV bus address. The

R/W bit must be a 0. The DS75LV responds with an ACK.

If the next byte is a 0x54, the DS75LV resets as if power

had been cycled. No ACK is sent by the IC after the POR

command is received.

Reading from the DS75LV: When reading from the

DS75LV, if the pointer was already pointed to the desired

register during a previous transaction, the read can be

performed immediately without changing the pointer setting.

In this case the master sends a START followed by an

address byte containing the DS75LV bus address. The

R/W bit must be a 1, which tells the DS75LV that a read

is being performed. After the DS75LV sends an ACK in

response to the address byte, the DS75LV begins trans-

mitting the requested data on the next clock cycle. When

reading from the configuration register, the DS75LV

transmits one byte of data, after which the master must

respond with a NACK followed by a STOP (see Figure

9e). For two-byte reads (i.e., from the Temperature, TOS

or THYST register), the DS75LV transmits two bytes

of data, and the master must respond to the first data

byte with an ACK and to the second byte with a NACK

followed by a STOP (see Figure 9a). If only the most

significant byte of data is needed, the master can issue

a NACK followed by a STOP after reading the first data

byte in which case the transaction is the same as for a

read from the configuration register.

If the pointer is not already pointing to the desired register,

the pointer must first be updated as shown in Figure 9d,

which shows a pointer update followed by a single-byte

read. The value of the R/W bit in the initial address byte

is a 0 (“write”) since the master is going to write a pointer

byte to the DS75LV. After the DS75LV responds to the

address byte with an ACK, the master sends a pointer byte

that corresponds to the desired register. The master must

then perform a repeated start followed by a standard one

or two byte read sequence (with R/W =1) as described in

the previous paragraph.

Bus Timeout: The DS75LV has a bus timeout feature

that prevents communication errors from leaving the IC

in a state where SDA is held low disrupting other devices

on the bus. If the DS75LV holds the SDA line low for a

period of tTIMEOUT, its bus interface automatically resets

and release the SDA line. Bus communication frequency

must be fast enough to prevent a reset during normal

operation. The bus timeout feature only applies to when

the DS75LV is holding SDA low. Other devices can hold

SDA low for an undefined period without causing the

interface to reset.

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