
17-22
DSP56853/854/855/857/858 User’s Manual
MOTOROLA
Preliminary
TAP Controller
17
17.8.1.5 Capture Data Register (pstate = 6)
In this controller state, data may be parallel loaded into test registers selected by the
current instruction on the rising edge of TCK. If a Test Data register selected by the
current instruction does not have a parallel input, the register retains its previous value.
17.8.1.6 Shift Data Register (pstate = 2)
In this controller state, the Test Data register is connected between TDI and TDO. This
data is then shifted one stage towards its serial output on each rising edge of TCK. The
TAP Controller will remain in this state while TMS is held at a low. When a one is applied
to TMS and a positive edge of TCK occurs the controller will move to the Exit1-DR state.
17.8.1.7 Exit1 Data Register (pstate = 1)
This is a temporary controller state. If TMS is held high, and a rising edge is applied to
TCK while in this state causes the controller to advance to the Update-DR state. This
terminates the scanning process.
17.8.1.8 Pause Data Register (pstate = 3)
This controller state allows shifting of the Test Data register in the serial path between
TDI and TDO to be temporarily halted. All Test Data registers selected by the current
instruction retain their previous state unchanged. The controller remains in this state while
TMS is held low. When TMS goes high and a rising edge is applied to TCK, the controller
advances to the Exit2-DR state.
17.8.1.9 Exit2 Data Register (pstate = 0)
This is a temporary controller state. If TMS is held high, and a rising edge is applied to
TCK while it is in this state, the scanning process terminates and the TAP Controller
advances to the Update-DR state. If TMS is held low and a rising edge of TCK occurs, the
controller advances to the Shift-DR state.
17.8.1.10 Update Data Register (pstate = 5)
All boundary scan register contain a two stage data register. It isolates the shifting and
capturing of data on the peripheral from what is applied to internal logic during scan
mode. This register is the second stage, or parallel output, and it is used to apply a stimulus
to internal logic. Data is latched on the parallel output of these Test Data registers from the
Shift register path on the falling edge of TCK in the Update-DR state. On a rising edge of
TCK, the controller advances to the Select_DR state if TMS is held high or the
Run-Test-Idle state If TMS is held low.