Implementation
Chip designers wishing to implement IEEE 1149.7 functionality in their devices can include a protocol converter on the device. The converter makes it simple to add basic IEEE 1149.7, such as reduced pin connectivity to existing IP that may only be compatible with IEEE 1149.1. For example, Figure 6 illustrates a sample two-core device with IEEE 1149.1 support. If chip designers want to add IEEE 1149.7 support, they simply include a protocol converter on the device. The benefit of doing this would be that the debug logic of Core A and Core B would not need to change. Also, since the IEEE 1149.7 system can also transport instrumentation data in the background, two more pins are reduced from the system, resulting in a device requiring only two functional pins, as shown in Figure 7.

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From Figure 7, it's also possible to use a protocol converter to allow existing IEEE 1149.1 systems to work with IEEE 1149.7 devices. This enables re-use of existing software and hardware infrastructure and lowers the entry cost for end users.

Two pins better than four
IEEE 1149.7 was created with several goals in mind--specifically to maintain backward compatibility with IEEE 1149.1 and improve debug performances. IEEE 1149.7 also reduces System-on-Chip (SoC) pin-count requirements and provides standardized power-saving operating conditions. The new standard also aims to simplify manufacturing of multichip modules and stacked-die devices and accommodates existing practices that deviate from the IEEE 1149.1 standard.

Stephen Lau is the product manager for emulation technology at Texas Instruments. His responsibilities include marketing, product definition (end-user product and IP), and managing strategic third-party partnerships and customers. You may reach Stephen Lau at s-lau2@ti.com.