The loopback test uses function code 08 (Hex.) and returns the command message as a response message. This test checks communication between the master and slave. The test code and data can use desired values. Table 1 shows examples of messages given out when the loopback test is done with the drive of slave 1. Table 1. Message Examples from the Loopback Test Byte Command Message Setting Data (Hex.) Response Message (Normal) Setting Data (Hex.) 0 Slave address 01 Slave address 01 1 Function code 08 Function code 08 2 Test code Upper 00 Test code Upper 00 3 Lower 00 Lower 00 4 Data Upper A5 Data Upper A5 5 Lower 37 Lower 37 6 CRC-16 Upper DA CRC-16 Upper DA 7 Lower 8D Lower 8D