pnx1700 NXP Semiconductors, pnx1700 Datasheet - Page 119

• Manufacturer Part Number: pnx1700
• Description: Connected Media Processor
• Manufacturer: NXP Semiconductors

Philips Semiconductors
Volume 1 of 1
PNX17XX_SER_1
Preliminary data sheet
5.3 The Master Semaphore
5.4 Usage Notes
Each PNX17xx Series in the system adds a block of 16 semaphores to the mix. The
intended use is to treat one of these block of 16 semaphores as THE master
semaphore block in the system. To determine which semaphore block is master each
TM5250 can use PCI configuration space accesses to determine which other
PNX17xx Seriess are present in the board system. Then, the PNX17xx Series with
the lowest PERSONALITY number, or the lowest MMIO_BASE is chosen as the
PNX17xx Series containing the master semaphores.
To avoid contention between the different tasks trying to access the different critical
resources of the system or the application, PNX17xx Series offers 16 different
semaphore devices. This allows to use them not only for inter-processor semaphores
but also for processes running on a single PNX17xx Series. However these process
synchronizations within the same processor can use regular memory to memory
transactions to implement primitive synchronization.
As described here, obtaining a semaphore does not guarantee starvation-free access
to critical resources. Claiming of one of the semaphores is purely stochastic. This
works fine as long as a particular semaphore is not overloaded. Despite a large
amount of available semaphores, utmost care should be taken in semaphore access
frequency and duration of the basic critical sections to keep the load conditions
reasonable.
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PCI configspace PERSONALITY entry. Each PNX17xx Series receives a 16-bit
PERSONALITY value from the EEPROM during boot. This PERSONALITY
register is located at offset 0x40 in configuration space. In a MP system, some of
the bits of PERSONALITY can be individualized for each CPU involved, giving it
a unique 2-, 3- or 4-bit ID, as needed given the maximum number of CPUs in the
design.
In the case of a host-assisted PNX17xx Series boot, the PCI BIOS assigns a
unique MMIO_BASE and DRAM_BASE to every PNX17xx Series. In particular,
the 11 MSBs of each MMIO_BASE are unique, since each MMIO aperture is 2
Megabytes in size. These bits can be used as a personality ID. Set bit 11 (MSB)
to '1' to guarantee a non-zero ID value.
Rev. 1 — 17 March 2006
Chapter 3: System On Chip Resources
© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
PNX17xx Series
3-10