基本特征：

DS26900是一款JTAG信号复用器，能够将3路主机端口之一连接到18路(36路级联配置)次级端口。该器件可以通过三个主机端口中的任意一路进行配置。DS26900可自动检测次级端口JTAG器件的连接状态。

方案特点：

Ribbon Cable Connectors for Master and
Secondary JTAG Port Connections
Jumpers for Device Configuration
LEDs for Device State Outputs
Simple Power Connections

The simplest configuration to test for communication with the DS26900 demo kit is to connect a JTAG source to master port 1, connect power, and, using JTAG sequences, manipulate some of the device state output LEDs on the board. The SSPIx LEDs can be used to verify that the desired secondary port is being selected. The GPIOx LEDs can be observed to verify that the GPIO pins are being correctly selected.

Some signals available at these

connectors can be controlled dynamically from the connector or from jumpers.
When driving a signal from the master port connectors the jumper can be removed or
placed in a pullup or pulldown position determined by the method of driving the signal.

参考原理图：

图1

图2

图3