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Chapter 20
CALRAM Operation
The calibration static random access memory (CALRAM) module provides the MPC533
with a general purpose memory that may be read from or written to as either bytes,
half-words, or words. In addition to this, a portion of the CALRAM, called the overlay
region, can be used for calibration. Calibration in this context is defined as overlaying
portions of the U-bus Flash with a portion of the CALRAM array. During normal Flash
access, the RISC central processing unit (RPCU) reads data from U-bus Flash (through
L-bus and L2U) as shown in Figure 20-1. During calibration access, instead of Flash
providing the data, the overlay regions of CALRAM provide the data to the RPCU.
20.1 Features
Standard CALRAM features are listed below:
• One-clock accesses
— Two-cycle access for power savings
• Byte, half-word (16-bits), or word (32-bit) read/write accesses
• Each 8-Kbyte block has individual protection control bits.
• Low power standby operation for data retention
Special overlay features are:
• Eight overlay regions; each can be programmed to be 4-, 16-, 32-, 64-, 128-, 256-,
or 512-bytes long
• Each overlay region size can be forced to 4 bytes long
• Data driven from the CALRAM module for overlay access has the same timing as
the data that would have come from the U-bus Flash
• Overlay is for data read from the U-bus Flash space and does not affect instruction
fetches from the Flash
• Overlay block is naturally aligned
— For example, 128-byte block is 128-byte aligned
• Normal access to overlaid portion of CALRAM array can be made to generate an
error (machine check) if so configured
MOTOROLA
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
Chapter 20. CALRAM Operation
20-1
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