Livt.Usb

src/packets/TokenCodec.lvt

namespace Livt.Usb.Packets

/**
 * Pure USB token field layout. CRC calculation remains a separate dependency.
 * SOF supplies its eleven-bit frame number directly instead of address/endpoint.
 */
component TokenCodec
{
	/**
	 * Packs seven address bits followed by four endpoint bits, transmitted LSB first.
	 */
	public static fn Fields[](address: logic[7], endpoint: logic[4]) logic[11]
	{
		return ((address as uint) | ((endpoint as uint) << 7)) as logic[11]
	}

	/**
	 * Appends five checksum bits; transmit the low byte before the high byte.
	 */
	public static fn Pack[](fields: logic[11], crc: logic[5]) logic[16]
	{
		return ((fields as uint) | ((crc as uint) << 11)) as logic[16]
	}

	/**
	 * Extracts the address of an IN/OUT/SETUP token.
	 */
	public static fn Address[](fields: logic[11]) logic[7]
	{
		return (fields & 0x7F) as logic[7]
	}

	/**
	 * Extracts the endpoint of an IN/OUT/SETUP token.
	 */
	public static fn Endpoint[](fields: logic[11]) logic[4]
	{
		return (fields >> 7) as logic[4]
	}
}