MSC8144E Reference Manual, Rev. 3
26-14
Freescale
Semiconductor
Security Engine (SEC)
26.2.2 Assignment of EUs to Channels
Assignment of an EU to a channel is done dynamically, as follows:
The channel requests an EU, the controller checks to see if the requested EU is available,
and if it is, the controller grants the channel assignment of the EU.
If an EU is available for a channel when requested, the controller asserts the grant signal
pertaining to the request from the channel. The grant signal remains asserted until the
channel is done and releases the EU.
In some cases, a channel may request two EUs. The channel does this by requesting the
primary EU and then requesting the secondary EU. Once the controller has granted both
EUs, this channel can request that the secondary EU snoop the bus. Snooping status is
indicated in the MI and MO bits of Channel Pointer Status Register (CPSR). See Section
26.5.5.2, Channel Pointer Status Registers (CPSR[1–4]) for details.
In all cases, the controller assigns the primary EU to a requesting channel as the EUs
become available. The controller does not wait until both EUs are available before issuing
any grants to a channel that requests two EUs.
Since there are multiple channels in the SEC, access to execution units through the channels must
have arbitration. The controller implements a snapshot arbiter for each EU. When access requests
occur, the arbiter records the set of pending requests (that is, it takes a snapshot) and then satisfies
those requests as the resource becomes available. When all requests in the snapshot are satisfied,
the arbiter takes another snapshot.
Within a given snapshot, the arbiters can use either a weighted priority-based scheme or a
round-robin scheme, depending on the values of the Channel 3 and Channel 4 EU priority count
fields in the Master Control Register. Each of these fields is 2-bits and can have a value from 0 to
3. If both fields have non-zero values, the arbiter implements the weighted priority scheme. If
both fields are 0, the arbiter uses the round-robin scheme. Having only one field with a zero value
results in unpredictable operation.
26.2.2.1 Weighted Priority Arbitration
The weighted priority scheme uses the following:
Channel 1—Highest priority
Channel 2—Second highest priority, the channel 3 or channel 4 priority has expired
Channel 3—Third priority, unless the channel 4 priority has expired.
Channel 4—Lowest priority, until the channel 4 priority expires.
Initially, the priority is channel 1, channel 2, channel 3, and channel 4, in that order. To prevent
channels 3 and 4 from always being locked out, the priority scheme uses the configured values in
the channel 3 and 4 priority fields in the Master Control Registers to determines how many times
channel 3 or channel 4 can be refused access to an EU in favor of a higher priority channel.
Содержание MSC8144E
Страница 1: ...MSC8144E Reference Manual Quad Core Media Signal Processor MSC8144ERM Rev 3 July 2009 ...
Страница 40: ...MSC8144E Reference Manual Rev 3 xl Freescale Semiconductor Contents 26 5 12 8 RNG Output FIFO 26 186 ...
Страница 48: ...MSC8144E Reference Manual Rev 3 xlviii Freescale Semiconductor ...
Страница 86: ...MSC8144E Reference Manual Rev 3 1 38 Freescale Semiconductor Overview ...
Страница 167: ...OCE Event and JTAG Test Access Port Signals MSC8144E Reference Manual Rev 3 Freescale Semiconductor 3 59 ...
Страница 168: ...MSC8144E Reference Manual Rev 3 3 60 Freescale Semiconductor External Signals ...
Страница 242: ...MSC8144E Reference Manual Rev 3 5 26 Freescale Semiconductor Reset ...
Страница 314: ...MSC8144E Reference Manual Rev 3 8 24 Freescale Semiconductor General Configuration Registers ...
Страница 414: ...MSC8144E Reference Manual Rev 3 10 14 Freescale Semiconductor MSC8144E SC3400 DSP Subsystem ...
Страница 452: ...MSC8144E Reference Manual Rev 3 11 38 Freescale Semiconductor Internal Memory Subsystem ...
Страница 520: ...MSC8144E Reference Manual Rev 3 12 68 Freescale Semiconductor DDR SDRAM Memory Controller ...
Страница 884: ...MSC8144E Reference Manual Rev 3 17 44 Freescale Semiconductor RapidIO Interface Dedicated DMA Controller ...
Страница 1070: ...MSC8144E Reference Manual Rev 3 21 28 Freescale Semiconductor Timers ...