HMC6352 Datasheet, PDF (4/13 Pages) Honeywell Solid State Electronics Center – Digital Compass Solution

HMC6352
address byte designates if the operation is a read (LSb=1) or a write (LSb=0). At the 9 ^th clock pulse, the recieving slave
device will issue the ACK (or NACK). Following these bus events, the master will send data bytes for a write operation, or
the slave will transmit back data for a read operation. All bus transactions are terminated with the master issuing a stop
sequence.
The following timing diagram shows an example of a master commanding a HMC6352 (slave) into sleep mode by sending
the “S” command. The bottom two traces show which device is pulling the SDA line low.
START 0 1
0 0 0 0 1 0 ^ACK 0 1
0 1 0 0 1 1 ACK STOP
SDA
SCL
M_SDA
S_SDA
42(hex)
Write to This I²C Address
“S”
Command
I²C bus control can be implemented with either hardware logic or in software. Typical hardware designs will release the
SDA and SCL lines as appropriate to allow the slave device to manipulate these lines. In a software implementation, care
must be taken to perform these tasks in code.
Command Protocol
The command protocol defines the content of the data (payload) bytes of I²C protocol sent by the master, and the slave
device (HMC6352).
After the master device sends the 7-bit slave address, the 1-bit Read/Write, and gets the 1-bit slave device acknowledge
bit returned; the next one to three sent data bytes are defined as the input command and argument bytes. To conserve
data traffic, all response data (Reads) will be context sensitive to the last command (Write) sent. All write commands shall
have the address byte least significant bit cleared (factory default 42(hex)). These commands then follow with the ASCII
command byte and command specific binary formatted argument bytes in the general form of:
(Command ASCII Byte) (Argument Binary MS Byte) (Argument Binary LS Byte)
The slave (HMC6352) shall provide the acknowledge bits between each data byte per the I²C protocol. Response byte
reads are done by sending the address byte (factory default 43(hex)) with the least significant bit set, and then clocking
back one or two response bytes, last command dependant. For example, an “A” command prompts the HMC6352 to
make a sensor measurement and to route all reads for a two byte compass heading or magnetometer data response.
Then all successive reads shall clock out two response bytes after sending the slave address byte. Table 1 shows the
HMC6352 command and response data flow.
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