All the frame information used for the UECP communication is defined by the specification. Each command is give a MEC and this is what the UECP encoder/decoder has to manipulate.
This an abbreviated list of MEC items. For a complete list the standard should be consulted:
| RDS Message Command | Message Element Code (MEC) | Message Element Purpose |
|---|---|---|
| PI | 0x01 | Program Identifier. A program specific type. |
| PS | 0x02 | Program Service. Identifies radio chain |
| TA/TP | 0x03 | Traffic Announcement/Traffic Program |
| DI | 0x04 | Decoder information. eg; set for a stereo program |
| MS | 0x05 | Message Service. Message service of the given data set |
| PIN | 0x06 | Program specific information. (See standard) |
| 7 | 0x07 | Program Type Information. |
| Real Time Clock Correction | 0x09 | Corrects the decoder clock for transmission delays. |
| RT | 0x0A | Radio Text. An informative text |
| Real Time Clock | 0x0D | Clock information in real time |
| Enable/Disable PSN | 0x0B | Enable/Disable usage of the PSN |
| RDS Level | 0x0E | Sets the RDS signal level in the MPX |
| GSS | 0x16 | Define a RDS group sequence for transmission |
| Request | 0x17 | Just that a request for information |
| Message Acknowledge | 0x18 | A reply to inform that the encoder has accepted a message |
| Enable/Disable RTC | 0x19 | Enable/Disable the transmission of group 4A information |
| DSS | 0x1C | Select a pre-defined data set for transmission |
| Enable/Disable RDS | 0x1E | Enable/Disable the transmission of RDS |
| RDS phase | 0x22 | Adjust RDS phase relative to MPX pilot |
| Site Address | 0x23 | Set the site address |
| Encoder Address | 0x27 | Set the encoder address |
| Make PSN | 0x28 | Make up a PSN list for the encoder |
| Private RDS command | 0x2D | Manufacture specific commands |
| PS select | 0x2F | Select the PS character code to be used in the transmission |
| PTYN | 0x3E | Program Type Name |
This list is not exclusive, there are many more commands. For more information consult the new draft specification under request for comments this year (2015)