Global Village A300.Md

# Global Village A300 ADB Modem Protocol This document contains experimentally-observed behavior of the Global Village A300 modem's ADB protocol. It contains enough information to satisfactorally emulate the serial port, however, many unknowns exist. The modem's default address may be 0x5 (observed on firmware 1.5) or 0x7 (observed on firmware 1.4) and its default handler ID is 0x36. Consistent with ADB standards, register 0 is the primary communications channel with the modem. ## Talk 0 A Talk 0 command will read status information or data received by the serial port. If no payload is received, there is no data or status to receive. If received, the payload is always eight bytes in length, and the eighth byte determines the meaning of the payload: | 8th Byte | Meaning | | --------- | ---------------------------------------------------------------------------------------------------------------------------- | | 0x00-0x7F | Payload contains 8 bytes received by serial port in 1st through 8th bytes | | 0x80 | Payload contains no data | | 0x81 | Payload contains 1 byte received by serial port in 1st byte, 2nd through 7th are invalid | | 0x82 | Payload contains 2 bytes received by serial port in 1st through 2nd bytes, 3rd through 7th are invalid | | 0x83 | Payload contains 3 bytes received by serial port in 1st through 3rd bytes, 4th through 7th are invalid | | 0x84 | Payload contains 4 bytes received by serial port in 1st through 4th bytes, 5th through 7th are invalid | | 0x85 | Payload contains 5 bytes received by serial port in 1st through 5th bytes, 6th through 7th are invalid | | 0x86 | Payload contains 6 bytes received by serial port in 1st through 6th bytes, 7th is invalid | | 0x87 | Payload contains 7 bytes received by serial port in 1st through 7th bytes | | 0x88 | Modem-to-Mac status A in 1st through 5th bytes, 6th and 7th are invalid | | 0x89 | Modem-to-Mac status B in 1st byte, 2nd through 7th are invalid | | 0x8A-0x8F | Undetermined | | 0x90-0x9F | Same as 0x80-0x8F but requests the Mac to hold off sending Listen 0 commands until a payload ending in 0x80-0x8F is received | | 0xA0-0xFF | Payload contains 8 bytes received by serial port in 1st through 8th bytes …