ADLINK aTCA-N700 - Manual (Page 30)

aTCA-RN720 User's Guide
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5 Architecture Overview
The aTCA-RN720 is composed of the several major components as illustrated in Figure 5-1: the
MMC, the CPLD, the Retimers, the I2C Block and the QSFP/SFP+s. The QSFP/SFP+ optic ports
and the Retimers GN2405A from Gennum play a major role in the data plane. The data plane
components are connected via the 10G Serdes interface, where 10Gbps data rate is supported
by a pair of Serdes lanes per port. Since the SFI signals according to SFF8431 specification are
not intended to travel over a backplane, the use of the timer with equalizer function is essential to
compensate the signals. The 40G interface XLAUI depends on four pairs of 10G Serdes links.
The equalizer function of the Retimer compensates any frequency dependent loss on the path to
extend the reachability of sensitive 10G signals on the board. The retimer function recovers clean
edges of the signal distorted due to unwanted reflections on the impedance mismatch points such
as the vias and the connectors along the traces on the board. The GN2405A on the board has
both functions. The GN2405A supports two ports, thereby the board needs six devices to support
twelve of 10G interfaces, which result in12 TX links from the front blade to the RTM and another
12 SFI RX links from the RTM to the front blade. At the center of the control functions, there
exists the Module Management Controller or the MMC. The MMC is responsible for the RTM
management and interfaces with the front blade IPMC via IPMB-L to exchange management
commands, and the FRU information and the status. The CPLD sits in between the MMC and the
devices to distribute the control signals such as Enable/Disable and Resets and collect various
signals for the MMC. The I2C HUBs inside the I2C Block are used to extend a limited I2C bus
from the Zone 3 connector to control many devices by duplicating its primary I2C Bus into
secondary I2Cs.
Port2
SFI (Rx)
Port1
Port4
Port5
Port6
IPMB_L
LMP I2C
MMC
CPLD
Service Port
LED
RST
RST
LOGIC
Zone 3
MUX
SFI (Tx)
SFI
SFI
LED Control
PWR
Mgmt.
GN2405
A
GN2405
A
SFI (Tx)
SFI (Rx)
Port3
Figure 5-1 aTCA-RN720 Architecture