Matrix Orbital PK202-24-USB - Manual (Page 30)

6.3 ROM Commands
The ROM commands allow a device to be singled out for communication or all devices to be included.
This manual only presents the three most used ROM commands. For a more detailed listing and description
of all the ROM commands, consult the data sheet for the 1-wire device being used.
•
Match ROM [55h]: To single out a device, the Match ROM command is used. After this com-
mand has been issued the 64-bit target address is transmitted in LSB to MSB order. Any device with
an address that doesn’t match will ignore all further communication until the next bus reset.
•
Skip ROM [CCh]: After this command, all devices will continue to listen and process the trans-
action. This is equivalent to broadcasting to all devices. This command is useful when probes need
to be informed to get their measurement ready. With this command all the probes can be instructed
simultaneously.
•
Read ROM [33h]: All devices will begin transmitting their address after this command. This
command will only succeed when there is one device on the bus. When multiple devices are present,
all devices will begin transmitting their addresses, overlapping each other. This command can be used
to determine if there is more than one device on the bus. After the address has been read back, if the
CRC is valid, there is only one device on the bus. Otherwise, there are multiple devices on the bus and
each address must be searched out.
6.4 Display 1-Wire functions
The transaction command allows data to be put onto the bus and read off the bus for transactions. And
the search command identifies all the devices on the bus for further communication.
6.4.1 Transaction command (254 C8 1 [flags] [Send Bits] [Recieve bits]
[Send data])
The transaction command will perform a single transaction on the 1-wire bus in this order;
1. Bus Reset.
2. Transmit data onto the bus.
3. Receive data from the bus.
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