Texas Instruments SLAU081 manual 2.6.2Legacy Connector

Host Communication

2.6.2Legacy 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

Pin No.	Signal	Pin No.	Signal
1	XF	2	DGND
3	CLKX	4	DGND
5	CLKR	6	DGND
7	DX	8	DGND
9	DR	10	DGND
11	FSX	12	DGND
13	FSR	14	DGND
15	Resvd	16	DGND
17	CLKS	18	DGND
19	TOUT	20	DGND

EVM Connector – J13

Pin No.	Signal	Pin No.	Signal
1	XF	2	DGND
3	CLKX	4	DGND
5	CLKR	6	DGND
7	DX	8	DGND
9	DR	10	DGND
11	FSX	12	DGND
13	FSR	14	DGND
15	Resvd	16	DGND
17	CLKS	18	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.

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