MPSSE是FTDI公司的高端产品(FT232H、FT2232D、FT2232H、FT4232H)所内置的多协议同步串行引擎(Multi-Protocol Synchronous Serial Engine)的简称。
基于该引擎，开发人员可以轻松的开发出USB转SPI/JTAG/I2C产品。
下表列出当前支持MPSSE的产品以及相关参数:
| 型号 | 通道数 | 最大USB速度 | 最大IO速度 |
|---|---|---|---|
| FT232H | 1 | 480 Mbps | 30 Mbps |
| FT2232D | 2 | 12 Mbps | 6 Mbps |
| FT2232H | 2 | 480 Mbps | 30 Mbps |
| FT4232H | 4 | 480 Mbps | 30 Mbps |
MPSSE的 MSB/LSB 和数据长度
参考自AN_135 第3.1节:
MSB/LSB & Data Length
The MPSSE commands configure communications to send and receive data with either the least significant bit or most significant bit first. Consult the datasheet of the target device to determine which is needed. It is important to recognize that the choice of MPSSE command determines in which direction the data will be transmitted.
The MPSSE commands operate on bytes, regardless of the orientation of the target device. For example, if a 93C46D EEPROM configured for 16-bit operation, byte 0 is transmitted first from the MPSSE queue and will be the most significant byte of the 16-bit word. Byte 1 is transmitted next, becoming the least significant byte.
Both byte- and bit-based MPSSE commands exist to accommodate devices that may not operate on 8-bit increments.
简而言之，MPSSE可以通过命令来配置一个Byte，是MSB先行还是LSB先行。具体位序应该参考目标器件以及通信协议。
参考文档:
http://www.ftdichip.com/Support/Documents/AppNotes/AN_135_MPSSE_Basics.pdf