This command is sent in response to receiving a sync1, if a passive transfer was started. The control value is mostly the SC register, except the addition of the double speed bit.
#BGB AND KIGB LINK UPDATE#
The receiving end can choose to ignore joypad changes, or update its button state accordingly.Īny bits and fields other than the ones used for a purpose MUST be 0 when sending, and MUST be ignored when receiving.īit 3: 1 if button is pressed, 0 if button is releasedīit 4-7: 0 (due to a bug in previous bgb versions, these bits can't be used in the future and must remain 0) Joypad change, for remote control of an emulator. A change of these fields indicates a different (incompatible) protocol used. The number in each header is the command number (value of b1) Timestamps are used so each side can, at the right times, wait for the remote side, for synchronization. Timestamps only contain the lowest 31 bits, the highest bit is always 0. Each side sends its own local timestamp in packets, and maintains the difference between its own timestamp, and the received timestamp.
If the received values don't match, the connection is dropped.īoth sides maintain a "timestamp", which is in 2 MiHz clocks (2^21 cycles per second). When the link is established, both sides send a "version" packet, and verify the received packet. Note that while the i1 field would typically be used for a timestamp, its actual usage depends on an individual command's description of fields. Literal values are decimal, or $ prefixed hexadecimal.Īll communication is in the form of 8 byte packets. When individual bits are referred to, bit 0 is the lowest bit. Also, keep in mind that due to the nature of TCP, packet boundaries are not guaranteed: multiple commands may be in a single TCP packet, and a command may be split over multiple TCP packets. The TCP_NODELAY setting should be set on the socket to avoid extra delays in the OS. When the initial handshake is complete, until the connection is broken, a plugged in link cable is emulated. one side listens, the other side connects. If this is no longer possible, the protocol version will be changed, and compatibility broken.īgb game link works over TCP/IP. It is the intention that this protocol keeps being used, with negotiation for new features as necessary, to maintain back and forward compatibility with older BGB versions (>= 1.4) and 3rd party implementations. Used in bgb versions 1.4.x and 1.5.x and possibly in later versions. Bgb 1.4 link protocol BGB 1.4 link protocol Back to main page
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