Motorola MPC8260 User Manual

26-2

MOTOROLA

Figure 26-1. SMC Block Diagram

The receive data source can be L1RXD if the SMC is connected to a TDM channel of an
SIx, or SMRXD if it is connected to the NMSI. The transmit data source can be L1TXD if
the SMC is connected to a TDM or SMTXD if it is connected to the NMSI.

If the SMC is connected to a TDM, the SMC receive and transmit clocks can be
independent from each other, as deÞned in Chapter 14, ÒSerial Interface with Time-Slot
Assigner.Ó However, if the SMC is connected to the NMSI, receive and transmit clocks
must be connected to a single clock source (SMCLK), an internal signal name for a clock
generated from the bank of clocks. SMCLK originates from an external signal or one of the
four internal baud rate generators. 

An SMC connected to a TDM derives a synchronization pulse from the TSA. An SMC
connected to the NMSI using transparent protocol can use SMSYN for synchronization to
determine when to start a transfer. SMSYN is not used when the SMC is in UART mode.

The following is a list of the SMCÕs main features:

¥

Each SMC can implement the UART protocol on its own signals

¥

Each SMC can implement a totally transparent protocol on a multiplexed or 
nonmultiplexed line. This mode can also be used for a fast connection between 
MPC8260s.

¥

Each SMC channel fully supports the C/I and monitor channels of the GCI (IOM-2) 
in ISDN applications

¥

Two SMCs support the two sets of C/I and monitor channels in the SCIT channels 0 
and 1

Shifter

SYNC

Rx

Data

Register

Tx

Data

Register

RXD

Control

Logic

TXD

Control

Registers

Shifter

Peripheral Bus

CLK

60x Bus