Freescale Semiconductor MPC8260 - Manual (Page 771)

MPC8260 PowerQUICC II Family Reference Manual, Rev. 2
Freescale Semiconductor 24-1
Chapter 24
SCC Transparent Mode
Transparent mode (also called totally transparent or promiscuous mode) provides a clear channel on which
the SCC can send or receive serial data without bit-level manipulation. Software implements protocols run
over transparent mode. An SCC in transparent mode functions as a high-speed serial-to-parallel and
parallel-to-serial converter.
Transparent mode can be used for serially moving data that requires no superimposed protocol, for
applications that require serial-to-parallel and parallel-to-serial conversion for communication among
chips on the same board, and for applications that require data to be switched without interfering with the
protocol encoding itself, such as when data from a high-speed time-multiplexed serial stream is
multiplexed into low-speed data streams. The concept is to switch the data path without altering the
protocol encoded on that data path.
Transparent mode is configured in the GSMR; see Section 20.1.1, “The General SCC Mode Registers
(GSMR1–GSMR4).” Transparent mode is selected in GSMR_H[TTX, TRX] for the transmitter and
receiver, respectively. Setting both bits enables full-duplex transparent operation. If only one is set, the
other half of the SCC uses the protocol specified in GSMR_L[MODE]. This allows loop-back modes to
DMA data from one memory location to another while data is converted to a specific serial format.
The SCC operations are asynchronous with the core and can be synchronous or asynchronous with other
SCCs. Each clock can be supplied from the internal baud rate generator bank, DPLL output, or external
pins.
The SCC can work with the time-slot assigner (TSA) or nonmultiplexed serial interface (NMSI) and
supports modem lines with the general-purpose I/O pins. Data can be transferred either the msb or lsb first
in each octet.
24.1 Features
The following list summarizes the main features of the SCC in transparent mode:
• Flexible buffers
• Automatic SYNC detection on receive
• CRCs can be sent and received
• Reverse data mode
• Another protocol can be performed on the other half of the SCC
• MC68360-compatible SYNC options