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MCM64Z836 Datasheet(PDF) 30 Page - Motorola, Inc |
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MCM64Z836 Datasheet(HTML) 30 Page - Motorola, Inc |
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30 / 34 page  MCM64Z836 •MCM64Z918 30 MOTOROLA FAST SRAM TAP CONTROLLER INSTRUCTION SET OVERVIEW There are two classes of instructions defined in the IEEE Standard 1149.1–1990; the standard (public) instructions and device specific (private) instructions. Some public instructions, are mandatory for IEEE 1149.1 compliance. Optional public instructions must be implemented in pre- scribed ways. Although the TAP controller in this device follows the IEEE 1149.1 conventions, it is not IEEE 1149.1 compliant because some of the mandatory instructions are not fully imple- mented. The TAP on this device may be used to monitor all input and I/O pads, but can not be used to load address, data, or control signals into the RAM or to preload the I/O buffers. In other words, the device will not perform IEEE 1149.1 EXTEST, INTEST, or the preload portion of the SAMPLE/PRELOAD command. When the TAP controller is placed in capture–IR state, the two least significant bits of the instruction register are loaded with 01. When the controller is moved to the shift–IR state the instruction register is placed between TDI and TDO. In this state, the desired instruction is serially loaded through the TDI input (while the previous contents are shifted out at TDO). For all instructions, the TAP executes newly loaded instructions only when the controller is moved to update–IR state. The TAP instruction sets for this device are listed in the following tables. STANDARD (PUBLIC) INSTRUCTIONS BYPASS The BYPASS instruction is loaded in the instruction regis- ter when the bypass register is placed between TDI and TDO. This occurs when the TAP controller is moved to the shift–DR state. This allows the board level scan path to be shortened to facilitate testing of other devices in the scan path. SAMPLE/PRELOAD SAMPLE/PRELOAD is an IEEE 1149.1 mandatory public instruction. When the SAMPLE/PRELOAD instruction is loaded in the instruction register, moving the TAP controller out of the capture–DR state loads the data in the RAMs input and I/O buffers into the boundary scan register. Because the RAM clock(s) are independent from the TAP clock (TCK), it is possible for the TAP to attempt to capture the I/O ring con- tents while the input buffers are in transition (i.e., in a metast- able state). Although allowing the TAP to sample metastable inputs will not harm the device, repeatable results can not be expected. RAM input signals must be stabilized for long enough to meet the TAPs input data capture setup plus hold time (tCS plus tCH). The RAMs clock inputs need not be paused for any other TAP operation except capturing the I/O ring contents into the boundary scan register. Moving the controller to shift–DR state then places the boundary scan register between the TDI and TDO pins. Because the PRELOAD portion of the command is not implemented in this device, moving the controller to the update–DR state with the SAMPLE/PRELOAD instruction loaded in the instruction register has the same effect as the pause–DR command. This functionality is not IEEE 1149.1 compliant. EXTEST EXTEST is an IEEE 1149.1 mandatory public instruction. It is to be executed whenever the instruction register, whatever length it may be in the device, is loaded with all logic 0s. EXTEST is not implemented in this device. IDCODE The IDCODE instruction causes the ID ROM to be loaded into the ID register when the controller is in capture–DR mode and places the ID register between the TDI and TDO pins in shift–DR mode. The IDCODE instruction is the default instruction loaded in at TRST assertion and any time the controller is placed in the test–logic–reset state. THE DEVICE SPECIFIC (PUBLIC) INSTRUCTION SAMPLE–Z If the HIGH–Z instruction is loaded in the instruction reg- ister, all DQ pins are forced to an inactive drive state (High–Z) and the bypass register is connected between TDI and TDO when the TAP controller is moved to the shift–DR state. THE DEVICE SPECIFIC (PRIVATE) INSTRUCTION NO OP Do not use these instructions; they are reserved for future use. Freescale Semiconductor, Inc. For More Information On This Product, Go to: www.freescale.com |
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