Before you can send data bytes, you must send control bytes to address the bus correctly. Setting the 7210 to talk and listen would not be addressing the bus correctly. A correctly addressed bus has one talker and one or more listeners. Here are the steps required to send a message to a device:
1. Assert Attention
2. Unlisten (0x3F)
3. MLAx, where X is the address of the device (0x20 | DevicePad)
4. MTAy, where Y is the your address (0x40 | ControllerPad)
5. Deasserte Attention
6. Transfer the data bytes