Freescale Semiconductor PowerQUICC MPC885 Reference Manual page 964

ATM Overview
36.2.1 Parameter RAM Conflicts
Operating serial ATM on SCC2-4 or the UTOPIA interface on SCC4 causes other peripherals to lose their
parameter RAM. For SCC2, the serial ATM parameters extend into the SPI parameter RAM. However, the
parameters for SPI can be relocated without the need for RAM-based microcode. The parameter RAM for
SCC3/SMC1 and SCC4/SMC2/PIP is affected in the same manner, however, these cannot be relocated.
36.2.2 IDMA2 Restriction
Because of internal system constraints, IDMA2 can only be used in level-sensitive mode when ATM is
enabled. This requires the user to set the RCCR[DR1M] bit.
36.2.3 UTOPIA Conflicts
The UTOPIA interface is implemented using the hardware of IDMA1 and the parameter RAM page of
SCC4. Therefore, if the UTOPIA port is used:
• SCC4 is unavailable due to the loss of parameter RAM page 4.
• IDMA1 is unavailable. (The DREQ0 signal is lost, and the IDMA1 event and mask registers
IDSR1 and IDMR1 are used for UTOPIA events.)
• Parallel interface port (PIP) is unavailable (due to the loss of the PIP handshake signals, see the
MPC885 User's Manual, MPC885UM/AD, Section 33.2.1, "Control Character Table, RCCM, and
RCCR")
In ESAR mode:
• In UTOPIA split bus mode, PCMCIA port A signals are unavailable. However in UTOPIA muxed
bus mode, the PCMCIA port A signals are still available on the PCMCIA port A pins.
In ESAR multi-PHY mode:
• The PHY address signals are multiplexed with the signals of both SMCs. However, when a PHY
address signal is not activated, the pin's other signal functions become available. For example, if
only three PHY address lines are used in a UTOPIA master application (supporting up to seven
PHYs), the SMC1 data signals are still available.
36.2.4 ATM Pace Controller (APC), APC Timer, and SCC4
The ATM pace controller (APC) uses the CPM general-purpose timer 4 to schedule ATM cells for
transmission. That is, CPM timer 4 becomes the APC timer and cannot be used as a general purpose timer.
The APC can be disabled simply by disabling the APC timer. However, because most ATM applications
use the APC, be aware of the following restrictions applying to SCC4 when using the APC:
• SCC4 is unavailable when the UTOPIA port is used.
• When not in UTOPIA mode, SCC4 can only be used for serial ATM or transparent operation.
A detailed explanation of the technical reasons for these restrictions is provided in
the APC Without Using SCC4 or UTOPIA."
available communications protocol, including serial ATM.
36-2
There are no restrictions on SCC1–3; they can run any
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Section 40.4, "Using
Freescale Semiconductor