DLE ACK0 (X'1070') is a positive acknowledgment to the previous block. At the line protocol level, a DLE STX (X'1002') is also a positive acknowledgment to the previous block. The DLE ETB that signals the end of the transmission block must be sent by command chaining a separate write CCW for those two bytes of data to the write CCW used to transmit the transmission block. Otherwise, a command reject will occur.