DS2409 Dallas Semiconducotr, DS2409 Datasheet - Page 4

• Manufacturer Part Number: DS2409
• Description: MicroLAN Coupler
• Manufacturer: Dallas Semiconducotr

DS2409
1-WIRE CRC GENERATOR Figure 4
CONTROL FUNCTION COMMANDS
The “Control Function Flow Chart” (Figure 5) describes the protocols necessary for controlling the main
and auxiliary output as well as the control output of the DS2409. The 1-Wire Function Control section
and the Coupler Function Control section combine to interpret the commands issued by the bus master
and create the correct control signals within the device. Depending on the complexity of function to be
exercised, the 1-byte command code may require one or two more bytes being sent by the bus master.
Switching one branch on implies that the other branch is automatically switched off. At power-on, both
branches are switched off. Each command flow includes at least one byte of feedback information for the
bus master to check if the command was understood and executed.
STATUS READ/WRITE [5Ah]
This command should be sent to the device after powering up unless the default settings are adequate for
the application. Following the command code, the bus master has to send the status control byte. The bus
master will then read the status info byte from the device. The confirmation byte is identical to the status
info byte. Tables 1 and 2 show the bit assignments in both bytes.
At power-on the device will be in the auto-control mode and the control output will be assigned to the
main output. The control output can be assigned to the auxiliary output by setting bit 6 of the status
control byte to a 1. For manual operation of the control output one has to select manual mode (bit 5 = 1).
The value of bit 7 of the status control byte will then determine the status of the control output. A 1 for bit
7 will make the transistor conducting, a 0 will turn it off (non-conducting). To change the status of the
device, both bits 3 and 4 of the status control byte have to be 0. Otherwise the settings will remain
unchanged. In any case, the status info byte will reflect the currently valid settings including the changes
that might have been made with the status control byte.
The status info byte allows the bus master to verify the actual status of each output (STAT,
active/inactive, on/off) and the static level at the main and auxiliary output (LEVL, 1 for normal, 0 in case
of a short). If a 1-Wire output is inactive and a low-going edge is encountered during this time, the
DS2409 will set the event flag (EVNT) the status info byte. Each output has its own event flag. The event
flags are cleared with the All Lines Off command. Bit 7 of the status info byte tells if the device is auto-
control mode or manual mode. Depending on the value of this bit, the information in bit 6 (CNTR.
STAT) either reports the association of the control output to a particular output (auto-control mode) or the
status of the transistor at the control output.
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