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5-2
MPC180E Security Processor User’s Manual
PRELIMINARY—SUBJECT TO CHANGE WITHOUT NOTICE
Arc Four Execution Unit Registers
5.1.1 Status Register
The AFEU Status Register, shown in Figure 5-1, contains seven bits of information. These
bits describe the state of the AFEU circuit and are all active-high.
Figure 5-1. Arc Four Execution Unit Status Register
Table 5-2 describes the AFEU Status Register fields.
0
24
25
26
27
28
29
30
31
Field
—
Input Buffer
empty
Full msg
done
Sub-msg
done
Permute
done
Initialize
done
IRQ
Busy
Reset
0000_0000_0000_0000
R/W
Read
Addr
0x401
Table 5-2. AFEU Status Register Field Descriptions
Bit
Name
Description
0–24
—
Reserved, should be cleared.
25
Input Buffer empty
Set when there is no data waiting in the AFEU Input Buffer. This can be used to monitor
when the AFEU is ready to receive the next sub-message while it is processing the
current sub-message. Writing to the Message register will clear this bit.
26
Full message done
Set when the last sub-message has been processed. This bit will remain set until a new
key is written. Reading from the Cipher register will clear this bit.
27
Sub-message done
Set when the sub-message has been processed. Once the next sub-message is written,
the AFEU will begin processing it and this bit will clear.
28
Permute done
Set once the memory is permuted with the key. Once the first sub-message is written, the
AFEU will begin processing the message and this bit will clear.
29
Initialize done
Set once memory initialization is complete. Once the key data and length is written, the
AFEU will begin permuting the memory and this bit will clear.
30
IRQ
Asserted whenever an interrupt is pending (if interrupts are enabled). The following
conditions will generate an interrupt:
Memory initialization done
Memory permutation done
Sub-Message processing done
Full Message processing done
The specific cause of the interrupt can be determined by reading the additional bits of the
status register.
Hardware interrupts are disabled following a reset. The IRQ bit in the status register is not
affected by masking hardware interrupts in the control register.
31
Busy
Asserted whenever the AFEU core is not in an idle state. Memory initialization or
permutation and message processing conditions will cause this bit to be set. The Busy bit
will be set during context writes/reads.
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Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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F
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sc
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le
S
e
m
ic
o
n
d
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c
to
r,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
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.
..