6.1.2 SPI_Write Command and its Response

The SPI_Write command (0x24) initiates an SPI write transaction. The command writes wDatLen bytes of data, vWrDtPac, to the SPI client device selected by the active SPI configuration.

This command is sent through Endpoint 0x06 (OUT). The response is read through Endpoint 0x86 (IN).

If the write data length exceeds the payload capacity of a single USB packet, multiple packets are used. The first packet contains up to 60 data bytes, and each additional packet containing up to 62 data bytes.

A response is provided after the initial command packet, after each continuation packet, and after the write transaction completes.

Table 6-4. `SPI_Write` - Command
Serial No.	Byte Index	Command		Description
1	0	`0x24`	Command code	Initiates the SPI write transaction
2	1	`0xAF`	Command code extension byte	Initiates the SPI write transaction
3	2	`L(wDatLen)`	Data length (lower byte)	Number of data bytes. Maximum length: 65,535 bytes
4	3	`H(wDatLen)`	Data length (upper byte)	Number of data bytes. Maximum length: 65,535 bytes
5	4	`b0(vWrDtPac)`	First data byte	The first 60 bytes
6	5	`b1(vWrDtPac)`	Second data byte
7-63	6-62	`...`	Additional data bytes
64	63	`b59(vWrDtPac)`	The 60^th data byte
65	Wait for the first response from the MCP2222 to determine whether the command is accepted. If the data length is more than 60 bytes, continue writing.
66	0	`0x24`	Repeat command code	Write is continued
67	1	`0xA0`	Write is continued	Write is continued
68	2	`b60(vDatPac)`	The 61^st data byte	The next 62 data bytes
69-126	3-62	`...`	Additional data bytes
127	63	`b121(vDatPac)`	The 122^nd data byte
128	Wait for the next response
129	If all data bytes are not written, continue writing, by repeating the above steps from serial number 66 to 128 until all data bytes are written. The final packet may contain fewer than 62 data bytes.
130	Continue polling for the write-completion response.

Table 6-5. `SPI_Write` - First Response
Byte Index	Response		Description
0	`0x24`	Return command code	Returns whether the `SPI_Write` command was accepted
1	`0x22`	Accepted - initiated	The command is accepted, and an SPI write is initiated
	`0x60`	Rejected – wrong parameters	The command is rejected because the parameters are invalid
	`0x64`	Rejected – SPI is busy	The command is rejected because the SPI module is busy

Table 6-6. `SPI_Write` - Subsequent Response After Every Packet Written
Byte Index	Response		Description
0	`0x24`	Return command code	The SPI write is continued
1	`0x22`	Accepted - write continued	The SPI write is continued
	`0x68`	Rejected – buffer full	The write buffer is full. Retry the same packet until it is accepted.
	`0x20`	Success – write completed	The `SPI_Write` transaction is completed