This document is a reference manual for the ARM9TDMI microprocessor. The ARM9TDMI includes the following features:
The option, selectable using the UNIEN signal, of using two unidirectional buses DD[31:0] and DDIN[31:0], instead of a single bidirectional data bus. This is described in Unidirectional/bidirectional mode interface.
The value returned by the JTAG TAP controller IDCODE instruction is the value present on the new TAPID[31:0] input bus. This allows the ID code to be easily changed for each chip design.