5.6. Test interface driver

The test interface driver, Ticbox, is an external module that drives the test interface lines to gain access to the AHB bus, and then applies test vectors from a test input file. This test input file is the output from a C program written with the TICTalk command language.

Before reading this section, you must be familiar with AMBA and its test interface protocol. If not, refer to the AMBA Specification for further information.

Figure 5.15 shows an interface diagram of the Ticbox module.

Figure 5.15. Ticbox module interface diagram

The main sections of this module are:

When the external system reset input has been deasserted, the Ticbox requests access to the system. This is done by asserting TESTREQA HIGH and TESTREQB LOW. The TIC then indicates when test mode has been entered by asserting TESTACK HIGH. When in test mode, the test input file is then read and translated by the Ticbox into AMBA test interface transactions, using the TESTREQA and TESTREQB signals.

The Ticbox applies test vectors to the system every time the TESTACK line indicates the system is ready. On read cycles the value is masked and then compared with the masked expected value given in the test vector file. An error message is given if the comparison fails. System testing ends when the end of the input vector file is reached, and the Ticbox indicates this by asserting both TESTREQA and TESTREQB LOW to end the simulation.

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