Transition Boards
28
Model 6476 User Guide
3 • System Architecture
Figure 10. Front/rear boards and backplane interface
Rear-panel I/O boards are 6U in width and are 80mm in depth. The 4U chassis provides an 80mm transition
module section. This section provides eight 6U x 80mm slots for cPCI transition modules.
All front-entry board features (handles, keying, alignment pin, EMC, etc.) are also utilized on the rear-entry
boards. The rear-panel I/O transition boards are “in-line” with the front-entry boards. This means that the
front panels of rear-panel I/O transition boards are reversed (mirrored) from the front boards. The top handles
are on the bottom and vice versa. The slot keying holes and hole labels in both the card guides and front panels
are upside down compared to the front boards and card guides.
The same connector pin labeling sequence is used on the rear I/O transition boards as on the front boards,
with the position numbers going from bottom to top. This is a mirror image of the front board’s layout orien-
tation. Using the same 1-for-1 pin mapping sequence eliminates confusion and I/O signal pin mapping prob-
lems. For example, pin A3 is the same on the front boards, on the rear I/O transition board, and on the
backplane.
Rear-panel I/O transition boards may have active components in some applications. Power can be applied
either through the I/O pins from the front board, or from the normal power and ground pins defined as part of
the J1/P1 and J2/P2 connector pin assignments.
POWER
CPU F
AIL
ALARM
SYSTEM
ETHERNET
A
ETHERNET
B
CALLS ACT
PMC
WAN POR
TS
1
2
3
4
ERROR
FRAME
RS232 CONFIG
READY
6U Transition module
Mid-plane
6U Front card
