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2-14
2.6.2 Legacy Connector
J12, J13, and J15 are three 2x20 headers daisy-chained together and are
collectively referred to as the legacy connector. The principle behind this
arrangement is to eliminate the confused and untidy custom cabling that is
typically present when connecting a legacy DSP to an EVM. This
daisy-chained connector method is flexible, robust, and makes it possible to
use a standard flat signal-cable assembly, improving reliability of
communications between host and EVM.
Two shorting bars are inserted in J12 and J15; these bars permit alternate pins
on J13 to be DGND. If the user has complete discretion over signal routing at
the host end, it is recommended that the host-end connector should reflect the
same pinout as J13.
However, if the host-end connector does not (or cannot) mirror the pinout for
J13, then some degree of signal-twisting is necessary. This is accomplished
on the EVM by removing the shorting bars on J12 and J15 and typically
wire-wrapping directly onto the appropriate header.
For example, if the host connector on the DSP has the pin assignment
described in the following table, then a 1:1 mapping is possible and the user
should plug a flat 20-way ribbon cable into J13.
Host Connector EVM Connector – J13
Pin No. Signal Pin No. Signal Pin No. Signal Pin No. Signal
1 XF 2 DGND 1 XF 2 DGND
3 CLKX 4 DGND 3 CLKX 4 DGND
5 CLKR 6 DGND 5 CLKR 6 DGND
7 DX 8 DGND 7 DX 8 DGND
9 DR 10 DGND 9 DR 10 DGND
11 FSX 12 DGND 11 FSX 12 DGND
13 FSR 14 DGND 13 FSR 14 DGND
15 Resvd 16 DGND 15 Resvd 16 DGND
17 CLKS 18 DGND 17 CLKS 18 DGND
19 TOUT 20 DGND 19 TOUT 20 DGND
However, if the host connector has a different signal pinout, the user should
remove the shorting bars from J12 and J15. A flat 20-way IDC ribbon cable can
still be used; in this case, the user should plug the connector into J12 of the
EVM. Since the cable is now plugged into J12, and all the signals on both sides
of the J12 pins are routed to adjacent connector pins (J13 and J15), the user
can typically wire-wrap the associated host signal to the relevant EVM signal.
The example shown below demonstrates the steps that must be taken to
reassign the connector and wire-wrap the correct signals.