Interface Configuration
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
42-7
2. Program the UTOPIA mode register (UTMODE).
3. Program PBPAR and PBDIR to enable TxClav and the MPHY address signals.
4. Program PDPAR and PDDIR as required.
5. Enable ATM and UTOPIA operation by setting PDPAR[ATM,UT].
6. Program PBPAR, PBDIR to enable RxClav.
The ATM controller starts searching for SOC and sets SRSTATE[SNC] as soon as the first SOC is found.
42.3
Serial ATM Configuration
Serial ATM operations use one or more SCCs and serial interfaces. This section describes the
configuration of registers for serial ATM operation.
42.3.1
RISC Controller Configuration Register (RCCR)
Unlike the UTOPIA ATM configuration, there is no specific requirement for setting RCCR[DRQP] if
serial ATM is used exclusively. It is good practice however to set RCCR[DRQP] to any value other than
0b00 to allow a higher priority for SCC transfers in case the IDMA functionality is used.
42.3.2
SCC Configuration for Serial ATM
To enable an SCC to operate in serial ATM mode, configure the SCC for transparent operation (because
GSMR_L[MODE] has no explicit ATM option) and clear MRBLR in the SCC’s parameter RAM. If
MRBLR is programmed with a non-zero value, the SCC operates in transparent mode.
Be sure to initialize the ATM parameters and data structures before enabling serial ATM operation because
transfers begin as soon as the SCC is enabled in the GSMR.
The following sections describe the programming of the SCC registers for serial ATM operation.
42.3.2.1
General SCC Mode Register (GSMR)
To configure an SCC as an ATM controller, program GSMR_H[TRX, TTX, CDP, CTSP, CDS, CTSS] (see
Section 21.2.1, “General SCC Mode Register (GSMR)”
). When the initialization sequence has been
completed, GMSR_L[ENR, ENT] must be set to enable receive and transmit functions (see
Section 21.4.3,
“SCC Initialization”
).
An SCC running serial ATM does not support mixed mode operation (in which the SCC transmitter is
configured for ATM transmissions and the receiver is in transparent mode, or vice versa).
42.3.2.1.1
Bit-Aligned Cell Delineation
Bit-aligned cell delineation is available for applications in which a byte-aligned synchronization signal is
not needed. To enable bit-aligned cell delineation, set GSMR_H[17] (in the TCRC field, bit 16 is a don’t
care). In the serial ATM configuration, TCRC is used to inform the cell delineation state machine that the
receiver should perform cell delineation on a bit-by-bit basis because no byte alignment signal is present.
The cell delineation state machine is described in.
Summary of Contents for PowerQUICC MPC870
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