Datasheet

MCP2221
DS20005292A-page 42  2014 Microchip Technology Inc.
3.1.8 I
2
C™ READ DATA
This command is used to read user-given data to the
I
2
C Slave device (whose address and speed are
specified by the STATUS/SET Parameters command).
The command will have the following effects:
•The I
2
C engine will send the “START” condition.
• The selected I
2
C slave address is sent next, and
the I
2
C engine will wait for the slave to send an
acknowledge bit.
• The user data is read next, and the I
2
C engine
sends the acknowledge bit to the slave.
• If the requested length is more than 60 bytes,
subsequent user bytes will be read from the I
2
C
slave on the bus.
• When the user data length (being sent on the bus)
reaches the requested length, the I
2
C engine will
send the “STOP” condition on the bus.
3.1.8.1 Responses
TABLE 3-26: COMMAND STRUCTURE
Byte
Index
Value Effect
00x91
I
2
C Read Data – command code
1 0x00 Requested I
2
C transfer length – 16-bit value – low byte
2 0x03 Requested I
2
C transfer length – 16-bit value – high byte
3-63 Don’t
care
TABLE 3-27: RESPONSE 1 STRUCTURE
Byte
Index
Value Effect
00x91
I
2
C Read Data – command code echo
1 0x00 Command completed successfully
0x01 I
2
C Engine is busy (command not completed)
2 0x03 Internal I2C Engine state (at the moment the command was issued) – useful for monitoring the
I
2
C Engine’s status
3-63 Don’t
care