cn8237 Mindspeed Technologies, cn8237 Datasheet - Page 360

• Manufacturer Part Number: cn8237
• Description: Atm Oc-12 Servicesar Plus With Xbr Traffic Management
• Manufacturer: Mindspeed Technologies

16.0 Electrical and Mechanical Specifications
16.1 Timing
Figure 16-11. Flight Time
16-12
Step 3 – Calculating the
SSRAM Access Speed
NOTE(S):
Not shown are series terminators located close to the source on all signals.
SAR
Calculate the SSRAM access speed in order for the SAR to have a minimum of
3 ns of data set-up:
to destination. The CN8237EVM card was measured for PCB signal propagation
delay which came in at 3.1 ns for 12 inches (or 30.5 cm) of trace. All local
memory signal traces are less than 3 inches (or 7.5 cm). The Flight Time for FT1
and FT2 was set at 0.8 ns each. (See
speed of 8.5 ns.
NOTE:
NOTE:
2 inches (or 5.08 cm), then the maximum SSRAM access speed could be 8.3 ns.
for SSRAMs)
T – DL – FT1 – FT2 – 3 ns = Max. access speed for SSRAM
FTn represents the signal flight time or signal propagation delay from source
Using the above design numbers yields the following:
15 ns – 2.625 ns – 0.8 ns – 0.8 ns – 3 ns = 7.775 ns (maximum access speed
The Samsung parts used on the CN8237EVM card have a maximum access
In this example, if all Local Memory PCB trace lengths are kept less than
CLK
This gives the design some exposure to failure should the memory chips
exceed an access speed of 7.775 ns.
A reduction in Flight Time gives direct relief to SSRAM access speed.
Mindspeed Technologies
ADDR/CNTRL/DATA
DL
ATM OC-12 ServiceSAR Plus with xBR Traffic Management
Figure
™
16-11.)
SSRAM
by_16
(4X)
28237-DSH-001-C
8237_162
CN8237