1. Status
| Direction | Data | Description |
| Tx transmit | ‘TT’ | ASCII character ‘T’ repeated twice |
| Rx receive | ‘TT’ + 10 status bytes | see the description of the status record total number of bytes to receive: 12 bytes |
2. Short status
| Direction | Data | Description |
| Tx | ‘??’ | |
| Rx | byte1 byte2 | State (see the description of the State record) ErrCode total number of bytes to receive: 2 bytes (’??’ not echoed!): |
3. Ready for communication?
| Direction | Data | Description |
| Tx | ‘Q’ | once only! |
| Rx | ’Q’ ’T’ ’E’ ’Y’ or none | one of the following: ok to communicate expecting the status (’T’) command error, send ’T’ to cancel error flag busy |
4. Reset the generator
| Direction | Data | Description |
| Tx | ’PP’ | |
| Rx | none |