CY8C54 CYPRESS [Cypress Semiconductor], CY8C54 Datasheet - Page 12

• Manufacturer Part Number: CY8C54
• Description: Programmable System-on-Chip (PSoC)
• Manufacturer: CYPRESS [Cypress Semiconductor]

Table 4-2. Cortex M3 CPU Registers (continued)
4.2 Cache Controller
The CY8C54 family adds an instruction cache between the CPU
and the Flash memory. This guarantees a faster instruction
execution rate. The Flash cache also reduces system power
consumption by requiring less frequent Flash access.
4.3 DMA and PHUB
The PHUB and the DMA controller are responsible for data
transfer between the CPU and peripherals, and also data
transfers between peripherals. The PHUB and DMA also control
device configuration during boot. The PHUB consists of:
There are two PHUB masters: the CPU and the DMA controller.
Both masters may initiate transactions on the bus. The DMA
channels can handle peripheral communication without CPU
intervention. The arbiter in the central hub determines which
DMA channel is the highest priority if there are multiple requests.
4.3.1 PHUB Features
Document Number: 001-55036 Rev. *A
PRIMASK
FAULTMASK A 1-bit interrupt mask register. When set, it
BASEPRI
CONTROL
A central hub that includes the DMA controller, arbiter, and
router
Multiple spokes that radiate outward from the hub to most
peripherals
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
Register
A 1-bit interrupt mask register. When set, it
allows only the nonmaskable interrupt (NMI) and
hard fault exception. All other exceptions and
interrupts are masked.
allows only the NMI. All other exceptions and
interrupts are masked.
A register of up to nine bits that define the
masking priority level. When set, it disables all
interrupts of the same or higher priority value. If
set to 0 then the masking function is disabled.
A 2-bit register for controlling the operating
mode.
Bit 0: 0 = privileged level in thread mode, 1 = user
level in thread mode.
Bit 1: 0 = default stack (MSP) is used, 1 =
alternate stack is used. If in thread mode or user
level then the alternate stack is the PSP. There
is no alternate stack for handler mode; the bit
must be 0 while in handler mode.
Description
PRELIMINARY
Table 4-3. PHUB Spokes and Peripherals
4.3.2 DMA Features
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 simul-
taneously, a fairness algorithm guarantees an interleaved
minimum percentage of bus bandwidth for priority levels 2
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.
When the fairness algorithm is disabled, DMA access is granted
based solely on the priority level; no bus bandwidth guarantees
are made.
PHUB Spokes
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 64k bytes
Large transactions may be broken into smaller bursts of 1 to
127 bytes
TDs may be nested and/or chained for complex transactions
Table 4-4
PSoC
0
1
2
3
4
5
6
7
after the CPU and DMA priority levels 0 and 1 have
®
5: CY8C54 Family Data Sheet
SRAM
IOs, PICU,
PHUB local configuration,
Clocks, IC, SWV, EEPROM,
programming interface
Analog interface and
USB, CAN,
DFB
UDBs group 1
UDBs group 2
EMIF
I
2
C,
Timers, Counters, and PWMs
Peripherals
trim,
Power
Decimator
Flash
manager,
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