![](http://datasheet.mmic.net.cn/330000/PM7329-BI_datasheet_16444382/PM7329-BI_76.png)
PM7329 S/UNI-APEX-1K800
DATASHEET
PMC-2010141
ISSUE 2
ATM TRAFFIC MANAGER AND SWITCH
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
62
10.7 Memory Port
Much of the configuration information that S/UNI-APEX-1K800 requires for
normal operation is accessed indirectly through the memory port, as the
configuration storage is tightly coupled to performance. Register arrays are
provided to allow access to the following memory apertures:
External Queue context
Internal Queue context
Internal Loop context
The memory port is primarily used for context setup, but may also be used for
diagnostic purposes. Features include
Control register allows the microprocessor to specify the aperture,
address, and length of the burst. Access to the internal loop context are
restricted to single long word accesses.
4-word burst write buffer with 8-bit overflow register, supporting writes of
up to 4 contiguous 34-bit words to valid apertures.
Masked write mechanism, which can be used to overwrite specific bits of
1 word without affecting other bits.
4-word burst read buffer with 8-bit overflow register, supporting reads of
up to 4 contiguous 34-bit words from valid apertures.
Memory port status provided in the low priority interrupt status register,
allowing for polling or for interrupt driven accesses to memory.
Memory is accessed using a 4-long word address in the control register, along
with 4 long-word enables. This approach allows non-contiguous bursts within a
4-long word section of memory, or to specify which long word is to be accessed
in single long word transfer. (For example, the first and third word of a section
may be modified without changing the second and fourth).
To compensate for the difference between the 34-bit context memory bus and
the 32-bit microprocessor bus, an 8-bit overflow register is provided for both
reads and writes. The overflow register represents the most significant 2 bits of
up to 4 words in a burst access. In this manner, 4 34-bit words can be accessed
using a 5-word burst on the microprocessor bus.