Freescale Semiconductor PowerQUICC MPC885 Reference Manual page 649

Powerquicc family

Table of Contents

Maximum aggregate receive and transmit bandwidth of all SCCs of approximately 22 Mbps at

25-MHz system frequency (depending on protocol), scaling up linearly with frequency. See

Appendix B, "Serial Communications Performance."

Maximum serial clocking rates of 12.5 MHz on a 25-MHz system

DPLL circuitry for clock recovery with NRZ, NRZI, FM0, FM1, Manchester, and Differential

Manchester (also known as Differential Bi-phase-L)

Clocks can be derived from a baud rate generator, an external pin, or DPLL

Data rate for asynchronous communication can be as high as 3.125 Mbps at 25 MHz

Supports automatic control of the RTS, CTS, and CD modem signals

Multi-buffer data structure for receive and send (the number of buffer descriptors (BDs) is limited

only by the size of the internal dual-port RAM—8 bytes per BD)

Deep FIFOs (SCC2–SCC4 FIFOs are 16 bytes each.)

Transmit-on-demand feature decreases time to frame transmission (transmit latency)

Low FIFO latency option for send and receive in character-oriented and totally transparent

Frame preamble options

Full-duplex operation

Fully transparent option for one half of an SCC (Rx/Tx) while another protocol executes on the

other half (Tx/Rx)—except for Ethernet and serial ATM operation

Echo and local loopback modes for testing

SCC Registers

Each SCC has a general SCC mode register (GSMR), a protocol-specific mode register (PSMR), a data

synchronization register (DSR), and a transmit-on-demand register (TODR). The SCC supporting

registers are described in the following sections.

General SCC Mode Register (GSMR)

Each SCC contains a general SCC mode register (GSMR) that defines options common to each SCC

regardless of the protocol. GSMR_L contains the low-order 32 bits; GSMR_H, shown in

contains the high-order 32 bits. Some GSMR operations are described in later sections. These registers are

affected by HRESET and SRESET.

Freescale Semiconductor

MPC885 PowerQUICC Family Reference Manual, Rev. 2

Serial Communications Controllers