External Bus Interface (EBI)
MPC5510 Microcontroller Family Reference Manual, Rev. 1
Freescale Semiconductor
29-3
Preliminary
•
Burst support (wrapped only)
NOTE
Because the MPC5510 has no cache, the core does not generate any burst
accesses; therefore the only burst accesses possible to the EBI are from the
DMA.
•
Bus monitor
•
Port size configuration per chip select (16 or 32 bits)
•
Configurable wait states
•
Configurable internal or external transfer acknowledge (TA) per chip select
•
Four chip-select (CS[0:3]) signals
•
Four write/byte enable (WE[0:3]) signals
•
Configurable bus speed modes (1/2 or 1/4 of system clock frequency) - up to 25 MHz maximum
bus frequency
•
Stop and module-disable modes for power savings
•
Optional automatic CLKOUT gating to save power and reduce EMI
•
Misaligned access support (for chip-select accesses only)
29.1.3
Modes of Operation
The mode of the EBI is determined by the MDIS, EXTM, and AD_MUX bits in the EBI_MCR. See
Section 29.3.2.3, “EBI Module Configuration Register (EBI_MCR)
,” for details. Configurable bus speed
modes and debug mode are modes that the MCU can enter, in parallel to the EBI being configured in one
of its module-specific modes.
29.1.3.1
Single Master Mode
In single-master mode, the EBI responds to internal requests matching one of its regions, but ignores all
externally-initiated bus requests. The MCU is the only master allowed to initiate transactions on the
external bus in this mode; therefore, it acts as a parked master and does not have to arbitrate for the bus
before starting each cycle. Single-master mode is entered when EXTM=0 and MDIS=0 in the EBI_MCR.
29.1.3.2
External Master Mode
External-master mode is supported for factory test use only.
29.1.3.3
Module Disable Mode
The module disable mode is used for MCU power management. The clock to the non-memory-mapped
logic in the EBI can be stopped while in module disable mode. Requests (other than to memory-mapped
logic) must not be made to the EBI while it is in module disable mode, even if the clocks have not yet been
shut off. In this case, the behavior is undefined. Module disable mode is entered when MDIS = 1 in the
EBI_MCR.
