SEC Lite Crypto-Channel
MPC885 PowerQUICC Family Reference Manual, Rev. 2
Freescale Semiconductor
50-13
used by the controller and channel for internal data movement. The SEC Lite device drivers allow the host
to create proper headers for each crypto-graphic operation. See
Chapter 49, “SEC Lite Descriptors,”
for a
full description of the descriptor header.
50.1.5.2
Descriptor Length/Pointer Pairs
The length and pointer fields represent one of seven data length/pointer pairs. Each pair defines a block of
data in system memory. The length field gives the length of the block in bytes. The maximum allowable
number of bytes is 32 Kbytes. A value of zero loaded into the length field indicates that this length/pointer
pair should be skipped and processing continue with the next pair.
The pointer field contains the address, in 8xx address space, of the first byte of the data block. Transfers
from the 8xx bus with the pointer address set to zero will have the length value written to the EU, and no
data fetched from the 8xx bus.
50.1.5.3
Next Descriptor Pointer
Following the length/pointer pairs is the ‘Next Descriptor’ field, which contains the pointer to the next
descriptor in memory. Upon completion of processing of the current descriptor, this value, if non-zero, is
used to request a 8xx burst read of the next-data-packet descriptor. This automatic load of the next
descriptor is referred to as descriptor chaining. Chapter 5, “Descriptors” contains a full description of the
next descriptor pointer.
NOTE
The next descriptor pointer address must be modulo-4 aligned if write back
is enabled as the method of DONE notification.
50.2
Interrupts
The crypto-channel can assert both DONE and ERROR interrupts to the controller. When the interrupt
generation conditions have been met, the crypto-channel will assert the appropriate interrupt. The status
of the registered crypto-channel interrupts are available in the controller interrupt status register. The
registered interrupts can cleared by writing to the controller interrupt clear register. The crypto-channel
does not have an internal interrupt mask bit and interrupts are always asserted to the controller. The
controller can be programmed to mask channel interrupts to the host via its interrupt mask register (IMR).
See
Section 51.1.1, “Interrupt Mask Registers (IMR).”
50.2.1
Channel Done Interrupt
The channel DONE interrupt is generated when the crypto-channel has completed processing of a single
descriptor or the end of a chain of descriptors and the channel DONE interrupt enable bit in the CCCR (see
Figure 50-1 on page 50-2) is set. Which one of these conditions is responsible for the interrupt depends
upon the state of the NOTIFICATION_TYPE bit in the control register, or the
DONE_NOTIFICATION_FLAG in the descriptor header.
Summary of Contents for PowerQUICC MPC870
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