External Bus Interface (EBI)
MPC5565 Microcontroller Reference Manual, Rev. 1.0
12-22
Freescale Semiconductor
12.4.1.5
Memory Controller with Support for Various Memory Types
The EBI contains a memory controller that supports a variety of memory types, including
•
Synchronous burst mode flash with external SRAM
•
Asynchronous/legacy flash with external SRAM and a compatible interface
Each CS bank is configured via its own pair of base and option registers. Each time an internal to external
bus cycle access is requested, the internal address is compared with the base address of each valid base
register (17 bits are masked). Refer to
. If a match is found, the attributes defined for this bank
in its BR and OR are used to control the memory access. If a match is found in more than one bank, the
lowest bank matched handles the memory access. For example, bank 0 is selected over bank 1.
Figure 12-7. Bank Base Address and Match Structure
A match on a valid calibration chip select register overrides a match on any non-calibration chip select
register, with CAL_CS[0] having the highest priority. Thus the full priority of the chip selects is:
CAL_CS[0]....CAL_CS[3] and then CS[0]....CS[3].
When a match is found on one of the chip select banks, all its attributes (from the appropriate base and
option registers) are selected for the functional operation of the external memory access, such as:
•
Number of wait states for a single memory access, and for any beat in a burst access
•
Burst enable
•
Port size for the external accessed device
Refer to
Section 12.3.1.6, “EBI Base Registers 0–3 (EBI_BRn) and EBI Calibration Base Registers 0–3
Section 12.3.1.7, “EBI Option Registers 0–3 (EBI_ORn) and EBI Calibration
Option Registers 0–3 (EBI_CAL_ORn)
,” for a full description of all chip select attributes.
When no match is found on any of the chip select banks, the default transfer attributes shown in
are used.
BA
[0]
Comp
BA
[1]
Comp
BA
[2]
Comp
BA
[3]
Comp
BA
[4]
Comp
• • •
BA
[15]
Comp
BA
[16]
Comp
AM
[0]
AM
[1]
AM
[2]
AM
[3]
AM
[4]
AM
[5]
• • •
AM
[6]
AM
[16]
• • •
A[0:16]
AM[0:16]
Match
Address Mask
Base Address
• • •
Содержание MPC5565
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