Chapter 21. IEEE 1149.1 Test Access Port (JTAG)
21-7
Instruction Register
Figure 21-7. General Arrangement for Bidirectional Pins
21.5 Instruction Register
The MCF5272 IEEE 1149.1 implementation includes the three mandatory public
instructions (EXTEST, SAMPLE/PRELOAD, and BYPASS), the optional public ID
instruction, plus two additional public instructions (CLAMP and HI-Z) defined by IEEE
1149.1. The MCF5272 includes a 4-bit instruction register without parity, consisting of a
shift register with four parallel outputs. Data is transferred from the shift register to the
parallel outputs during the update-IR controller state. The 4 bits are used to decode the
instructions in Table 21-2.
The parallel output of the instruction register is reset to 0001 in the test-logic-reset
controller state. Note that this preset state is equivalent to the ID instruction.
Table 21-2. Instructions
B[3:0]
Instruction
Description
0000
EXTEST
The external test (EXTEST) instruction selects the boundary scan register. EXTEST asserts
internal reset for the MCF5272 system logic to force a predictable benign internal state while
performing external boundary scan operations.
By using the TAP, the register is capable of a) scanning user-defined values into the output
buffers, b) capturing values presented to input pins, c) controlling the direction of bidirectional
pins, and d) controlling the output drive of three-state output pins. For more details on the
function and uses of EXTEST, please refer to the IEEE 1149.1 document.
0001
ID
During the capture-IR controller state, the parallel inputs to the instruction shift register are
loaded with the 4-bit binary value (0001). The parallel outputs, however, remain unchanged
by this action since an update-IR signal is required to modify them.
IO.CELL
FROM LAST CELL
OUTPUT
DATA
INPUT
DATA
OUTPUT
ENABLE
I/O
PIN
TO NEXT CELL
*
NOTE: More than one lO.Cell could be serially connected and controlled by a single En.Cell.
EN.CELL
*
DIRECTION
OUTPUT
ENABLE
Содержание DigitalDNA ColdFire MCF5272
Страница 1: ...MCF5272UM D Rev 0 02 2001 MCF5272 ColdFire Integrated Microprocessor User s Manual ...
Страница 38: ...xxxviii MCF5272 User s Manual TABLES Table Number Title Page Number ...
Страница 58: ...1 10 MCF5272 User s Manual MCF5272 Specific Features ...
Страница 90: ...2 42 MCF5272 User s Manual Exception Processing Overview ...
Страница 96: ...3 6 MCF5272 User s Manual MAC Instruction Execution Timings ...
Страница 158: ...5 46 MCF5272 User s Manual Motorola Recommended BDM Pinout ...
Страница 184: ...7 12 MCF5272 User s Manual Interrupt Controller Registers ...
Страница 338: ...13 44 MCF5272 User s Manual Application Examples ...
Страница 414: ...18 6 MCF5272 User s Manual PWM Programming Model ...
Страница 452: ...19 38 MCF5272 User s Manual Power Supply Pins ...
Страница 482: ...20 30 MCF5272 User s Manual Reset Operation ...
Страница 492: ...21 10 MCF5272 User s Manual Non IEEE 1149 1 Operation ...
Страница 548: ...INDEX Index 12 MCF5272 User s Manual ...