DS1050
The command operation “Set Shutdown Mode” is used to provide a low-current (inactive state) state for
the DS1050. When in a low-current state the DS1050 will draw currents less than or equal to 1ꢀA. The
PWMO output will be high impedance.
The command operation “Set Recall Mode” is used to recall the DS1050 from a low-current state. The
value of the PWMO output is recalled to that prior to initiating a “Set shutdown mode” command.
The “Read PWM Duty Cycle” command is used to read the current setting of the PWM configuration
register. Information returned by this command includes PWM output value as well as whether the device
is in a shutdown configuration.
PWM data values and control/command values are always transmitted most significant bit (MSB) first.
During communications, the receiving unit always generates the “acknowledge.”
READING THE DS1050
As shown in Figure 4e, the DS1050 provides one read command operation. This operation allows the
user to read the current setting of the PWM configuration register. Specifically, the R/W bit of the
command/control byte is set equal to a 1 for a read operation. Communication to read the DS1050 begins
with a START condition which is issued by the master device. The command/control byte from the
master device will follow the START condition. Once the command/control byte has been received by
the DS1050, the part will respond with an ACKNOWLEDGE. The read/write bit of the command/control
byte, as stated, should be set equal to 1 for reading the DS1050.
When the master has received the ACKNOWLEDGE from the DS1050, the master can then begin to
receive the PWM configuration register data. As mentioned this data will be transmitted MSB first. Once
the eight bits of the PWM configuration register have been transmitted, the master will need to issue an
ACKNOWLEDGE, unless it is the only byte to be read, in which case the master issues a NOT
ACKNOWLEDGE. If desired the master may stop the communication transfer at this point by issuing the
STOP condition. Final communication transfer is terminated by issuing the STOP command. Again, the
flow of the read operation is presented in Figure 4e.
WRITING THE DS1050
A data flow diagram for writing the DS1050 is shown in Figures 4a, b, c, and d. The DS1050 has three
write commands that are used to change the PWM configuration register or the shutdown and recall mode
of the device.
All the write operations begin with a START condition. Following the START condition, the master
device will issue the command/control byte. The read/write bit of the command/control byte will be set to
“0” for writing the DS1050. Once the command/control byte has been issued and the master receives the
acknowledgment from the DS1050, PWM configuration data is transmitted to the DS1050 by the master
device.
A data byte for the DS1050 will contain PWM configuration data and shutdown/recall command data.
The five least significant bits of data specify the PWM configuration value while the three most
significant bits specify the whether the device is to be shutdown or recalled. When the DS1050 has
received the data byte, it will respond with an ACKNOWLEDGE. At this point, the new PWM
configuration register value and shutdown/recall command value will be updated in the DS1050. The
master device, after the receipt of the ACKNOWLEDGE, can continue to transmit additional data bytes
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DALLAS [ DALLAS SEMICONDUCTOR ]
