CY8C5246AXI-038 Cypress Semiconductor Corp, CY8C5246AXI-038 Datasheet - Page 12

• Manufacturer Part Number: CY8C5246AXI-038
• Manufacturer: Cypress Semiconductor Corp

Specifications of CY8C5246AXI-038

• Lead Free Status / RoHS Status: Compliant

4.3.1 PHUB Features
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Table 4-3. PHUB Spokes and Peripherals
4.3.2 DMA Features
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4.3.3 Priority Levels
The CPU always has higher priority than the DMA controller
when their accesses require the same bus resources. Due to the
system architecture, the CPU can never starve the DMA. DMA
channels of higher priority (lower priority number) may interrupt
current DMA transfers. In the case of an interrupt, the current
transfer is allowed to complete its current transaction. To ensure
latency limits when multiple DMA accesses are requested
simultaneously, a fairness algorithm guarantees an interleaved
minimum percentage of bus bandwidth for priority levels 2
Document Number: 001-55034 Rev. *G
PHUB Spokes
CPU and DMA controller are both bus masters to the PHUB
Eight multi-layer AHB bus parallel access paths (spokes) for
peripheral access
Simultaneous CPU and DMA access to peripherals located on
different spokes
Simultaneous DMA source and destination burst transactions
on different spokes
Supports 8-, 16-, 24-, and 32-bit addressing and data
24 DMA channels
Each channel has one or more transaction descriptors (TDs)
to configure channel behavior. Up to 128 total TDs can be
defined
TDs can be dynamically updated
Eight levels of priority per channel
Any digitally routable signal, the CPU, or another DMA channel,
can trigger a transaction
Each channel can generate up to two interrupts per transfer
Transactions can be stalled or canceled
Supports transaction size of infinite or 1 to 64 k bytes
Large transactions may be broken into smaller bursts of 1 to
127 bytes
TDs may be nested and/or chained for complex transactions
0
1
2
3
4
5
6
7
SRAM
IOs, PICU,
PHUB local configuration,
Clocks, IC, SWV, EEPROM,
programming interface
Analog interface and
USB, CAN,
Reserved
UDBs group 1
UDBs group 2
EMIF
I
2
C,
Timers, Counters, and PWMs
Peripherals
trim,
Power
Decimator
PRELIMINARY
Flash
manager,
through 7. Priority levels 0 and 1 do not take part in the fairness
algorithm and may use 100% of the bus bandwidth. If a tie occurs
on two DMA requests of the same priority level, a simple round
robin method is used to evenly share the allocated bandwidth.
The round robin allocation can be disabled for each DMA
channel, allowing it to always be at the head of the line. Priority
levels 2 to 7 are guaranteed the minimum bus bandwidth shown
in
satisfied their requirements.
Table 4-4. Priority Levels
When the fairness algorithm is disabled, DMA access is granted
based solely on the priority level; no bus bandwidth guarantees
are made.
4.3.4 Transaction Modes Supported
The flexible configuration of each DMA channel and the ability to
chain multiple channels allow the creation of both simple and
complex use cases. General use cases include, but are not
limited to:
4.3.4.1 Simple DMA
In a simple DMA case, a single TD transfers data between a
source and sink (peripherals or memory location).
4.3.4.2 Auto Repeat DMA
Auto repeat DMA is typically used when a static pattern is
repetitively read from system memory and written to a peripheral.
This is done with a single TD that chains to itself.
4.3.4.3 Ping Pong DMA
A ping pong DMA case uses double buffering to allow one buffer
to be filled by one client while another client is consuming the
data previously received in the other buffer. In its simplest form,
this is done by chaining two TDs together so that each TD calls
the opposite TD when complete.
4.3.4.4 Circular DMA
Circular DMA is similar to ping pong DMA except it contains more
than two buffers. In this case there are multiple TDs; after the last
TD is complete it chains back to the first TD.
4.3.4.5 Indexed DMA
In an indexed DMA case, an external master requires access to
locations on the system bus as if those locations were shared
memory. As an example, a peripheral may be configured as an
SPI or I
master. That address becomes an index or offset into the internal
system bus memory space. This is accomplished with an initial
Table 4-4
PSoC
Priority Level
2
C slave where an address is received by the external
0
1
2
3
4
5
6
7
after the CPU and DMA priority levels 0 and 1 have
®
5: CY8C52 Family Datasheet
% Bus Bandwidth
100.0
100.0
50.0
25.0
12.5
6.2
3.1
1.5
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