Extended APDU Format

Any APDU classified as extended must follow the format defined by ISO/IEC 7816-4:2013 for extended length APDU and summarized in the following table.

Table 8-1 Extended APDU Format

Field	Description	Number of Bytes
Command Header	Class byte CLA	1
Command Header	Instruction byte INS	1
Command Header	Parameter bytes P1- P2	2
LC Field	Absent for Nc = 0. Present for Nc > 0	0, 1, or 3
Data Field	Absent if Nc = 0, present if Nc >0	Nc
LE Field	Absent for Ne = 0, present for Ne > 0	0, 1, 2 or 3
Response Data	Absent if Nr = 0, present if Nr >0	Nr (max. Ne)
Response Status	Status bytes SW1 SW2	2

Notation

Nc = command data length

Ne = expected response data length

Nr = actual response data length

The encoding rules are defined as:

For LC:

• If LC field is absent, Nc = 0.

• If LC is present as one byte with values between 01 and FF, then Nc = 1..255 accordingly, and it will be a short field.

• If LC is present as an extended field, then it will be three bytes in length: byte one will be 00, bytes two and three will contain a 16-bit value representing the length of the data Nc with values between 1 and 65535.

For LE:

• If LE is absent, Ne = 0.

• If LE is one byte:

  • A value between 01 and FF will indicate Ne = 1..255.

  • A value of 00 will indicate Ne = 256.

If LE is an extended field:

• LC and LE must be in the same format.

• An LE field value between 0001 and FFFF will indicate Ne = 1..65535.

• An LE field value of 0000 will indicate Ne= 65536.