5.1.3 I2C_Read Command and its Response

The I2C_Read command (0x48) initiates an I²C read transaction. The command reads wRdDtLen bytes of data from the I²C client device addressed by bAddress.

This command is sent through Endpoint 0x03 (OUT) and the response is read through Endpoint 0x83 (IN).

Depending on the requested read length, multiple response packets may be returned. The first response may contain up to 60 data bytes and subsequent response packets may contain up to 62 data bytes each.

Table 5-7. `I2C_Read` - Command
SI. No.	Byte Index	Command		Description
1	0	`0x48`	Command code	Initiates the I²C read transaction
2	1	`bAddress`	I²C client address	7-bit I²C client address
3	2	`L(wRdDtLen)`	Read data length (lower byte)	Number of data bytes; maximum length 65535 bytes
4	3	`H(wRdDtLen)`	Read data length (upper byte)	Number of data bytes; maximum length 65535 bytes
5	Wait for the first response from the MCP2222 to determine whether the command is accepted
6	If accepted, continue reading until the required number of bytes are read or until a failure occurs.

Table 5-8. `I2C_Read` - First Response
Byte Index	First Response		Description
0	`0x48`	Return command code	Returns whether the `I2C_Read` command was accepted.
1	`0x22` `0x60` `0x64`	Accepted – initiated Rejected – wrong parameters Rejected – I²C is busy	The command is accepted and the read transaction is initiated. The command is rejected because the parameters are invalid. The command is rejected because the I²C module is busy.

Table 5-9. `I2C_Read` - Second Response
Byte Index	Second Response		Description
0	`0x48`	Return command code	The I²C read is continued.
1	`0x21`	Read is continued	The I²C read is continued.
	`0x80`	Failure - address NACK	An address NACK was received. Verify the I²C client address.
	`0x88`	Failure - clock-stretch timeout	A clock-stretch timeout occurred. Recover the bus and retry, if required.
	`0x8C`	Failure - arbitration lost	Bus arbitration was lost; another I²C host may be using the bus.
	`0x90`	Failure - an I²C bus error occurred	A bus error occurred.
2	`L(wRdDtLen)`	Data length (lower byte)	Number of data bytes to be read (maximum 65,535 bytes).
3	`H(wRdDtLen)`	Data length (higher byte)	Number of data bytes to be read (maximum 65,535 bytes).
4	`b0(vDatPac)`	First data byte	The first 60 data bytes are read
5	`b1(vDatPac)`	Second data byte
…	`...`	...
63	`b59(vDatPac)`	The 60^th data byte

Table 5-10. `I2C_Read` - Subsequent Responses
Byte Index	Subsequent Responses		Description
0	`0x48`	Return command code	The I2C_Read is continued
1	`0x21`	Read is continued	The I2C_Read is continued
	`0x88`	Failure - clock-stretch timeout	A clock-stretch timeout occurred. Recover the bus and retry, if required.
	`0x8C`	Failure - arbitration lost	Bus arbitration was lost
	`0x90`	Failure - an I²C bus error occurred	A bus error occurred
2	`b60(vDatPac)`	The 61^st data byte	The next 62 data bytes are read
…	`…`	...
63	`b121(vDatPac)`	The 122^nd data byte
Repeat the subsequent response sequence until all requested bytes have been received or an error occurs.