![](http://datasheet.mmic.net.cn/330000/PM73122_datasheet_16444367/PM73122_184.png)
RELEASED
PM73122 AAL1GATOR-32
DATASHEET
PMC-1981419
ISSUE 7
32 LINK CES/DBCES AAL1 SAR PROCESSOR
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
159
11.5 RAM Interface Block (RAMI)
The RAMI is the central arbiter for all memory accesses. It provides a priority
mechanism that incorporates fairness to satisfy all real-time requirements of the
various blocks. All blocks requesting a data transfer with the common memory
supply the address, control signals, and the data, if the requested data transfer is
a write, to the RAMI. When the RAMI actually grants the transfer, it provides a
grant signal to the requesting block, indicating that the transfer has been
performed. The memory is arbitrated on a cycle-by-cycle basis. No device is
granted the bus for an indefinite time.
The AAL1gator-32 has a separate SSRAM and processor interface. Either one or
two 256K x 16 or 256K x 18 SSRAMs are needed, depending on the mode of
operation. If using the SBI interface, or the upper four 8 Mbps MVIP interfaces,
or the upper two High speed interfaces, two rams are required
Either a pipelined synchronous SRAM with a single cycle deselect or a pipelined
ZBT or ZBT-compatible synchronous SRAM can be used.
For most applications the pipelined single-cycle deselect SSRAM is sufficient,
but if additional performance is needed, such as in cross connect applications
which need to use partial cells to lower delay, the ZBT SSRAM is recommended.
The SSRAM interface runs at the same frequency as SYS_CLK and can run up
to 45 MHz.
11.6 Line Interface Block (AAL1_LI)
11.6.1 Conventions
The following conventions are used in this document:
The 32 lines, which connect the AAL1_LI to the A1SP blocks, are called
local
links
. The lines on the external interface are called
external
lines
.
The direction from the local links to the external line interface is call the
transmit
direction. The direction from the external line interface to the local links is called
the
receive
direction.
The individual data streams within the SBI interface are known as
tributaries
.
Once inside the AAL1_LI, these data streams are known as
links
. In SBI mode
links and tributary numbering starts at ‘1’.
With respect to the SBI interface the
Add
direction is the one where data is
placed onto the SBI, the
Drop
direction is the one where data is extracted from