SBI Bus Serializer ASSP Telecom Standard Product Data Sheet
Released
Proprietary and Confidential to PMC-Sierra, Inc., and for its customers’ internal use.
Document No.: PMC-2000168, Issue 5
338
14
Functional Timing
14.1 Incoming SBI336 Bus Functional Timing
Figure 30 shows the functional timing for the incoming SBS 77.76MHz SBI336 bus configured
for connection to a physical layer device. When configured for the SBI336 bus timing is
provided by a 77.76MHz SREFCLK which is also connected to SYSCLK. When connecting to
a physical layer device the justification request signal, JUST_REQ, is used by the physical layer
device to control link timing from a slave link layer device and is an input to the SBS.
Figure 30 shows a number of capabilities of the SBI bus. IC1FP is a 2KHz pulse that indicates
the SBI336 frame alignment from which all control signals and data are synchronized. The
payload signal indicates valid tributary data as well as positive and negative tributary timing
adjustments. In Figure 30 the first occurrence of IPL[1] high shows a negative timing
adjustment where valid data is carried in the V3 location. The last cycle with IPL[1] low
indicates a positive timing adjustment in the tributary octet after V3 where there is no valid data.
The IV5[1] signal indicates that the current data octet is the V5 octet used for tributary framing
alignment. The JUST_REQ[1] signal is only valid during the V3 octets and the tributary octets
following the V3 octets. The first occurrence of JUST_REQ[1] high during the V3 octet
indicates to the slave link layer device that it should speed next frame by performing a negative
timing adjustment. The second occurrence of JUST_REQ[1] high during the tributary octet
after the V3 octet indicates to the slave link layer device that it should slow down by performing
a positive timing adjustment during the next frame. The last V3 in the diagram is meant to be
the last V3 for all the tributaries.
The ICMP signal selects the active connection memory page in the memory switch. It is
sampled at the C1 byte position in every multi-frame. ICMP is ignored at all other positions
within the SBI frame. The connection memory page is switched on the next SBI bus multi-
frame boundary after ICMP is sampled. The SBI multi-frame can be either 4 or 48 frames,
depending on the value of MF_48 in the SBS Master Configuration Register.
Figure 30 Incoming SBI336 Functional Timing
C1
V3
V3
DS0#9 V3
DS0#4 V5
DS0#2DS0#7
valid
SREFCLK
IC1FP
IPL[1]
IV5[1]
IDATA[1][7:0]
IDP[1]
JUST_REQ[1]
ICMP