12-20
ColdFire CF4e Core User’s Manual
For More Information On This Product,
Go to: www.freescale.com
BIST
12.3.3 Power Analysis
To maximize testing capabilities, reduce design time, and prevent potential brown-out
conditions that could occur if too many memories are switching simultaneously, it is critical
to analyze power considerations when memories are tested in parallel. Packaging can also
affect power considerations. The reference design has a potential of eight memories:
Operand cache unit (OCU) tag
OCU data
Instruction cache unit (ICU) tag
ICU data
RAM 0
RAM 1
ROM 0
ROM 1 array
Caches can be from 2 to 32 Kbytes. RAMs and ROMs can be 512 bytes to 64 Kbytes. Based
on BIST controller operation, memory size is independent. If an array is 8 or 32 Kbytes,
only one 2-Kbyte 512 x 32 SRAM block is active at a time; 2-Kbyte basic memory blocks
are assumed.
Pins and internal core logic not used for BIST (that is, all signals not in Table 12-3) are set
to a quiescent state during initialization, so BIST power consumption is negligible
compared to functional operation.
12.3.4 Staging of Memories
If the number of memories to be tested warrants parallel-sequential testing, memories are
split into two groups and one is tested first. After all memories in the first group are tested
(logical AND of all controller bistdone signals) with no failures, the second group is tested.
A similar approach is used to test data retention, using an output signal for each array
bistrelease
Input
PBIST/
EBIST
Used to release memories from hold state during data retention. If data
retention testing is not desired, assert this signal for the entire test.
bistmemory[2:0]
Input
EBIST
Selects which memory is characterized.
000 Data cache tag
001 Data cache data
010 Instruction cache tag
011 Instruction cache data
100 RAM 0
101 RAM 1
110 ROM 0
111 ROM 1
Table 12-3. BIST Core Pins (Continued)
Port Name
I/O
BIST Mode
Description
F
Freescale Semiconductor, Inc.
n
.