Advance
576Mb: x18, x36 RLDRAM 3
IEEE 1149.1 Serial Boundary Scan (JTAG)
TAP Controller
The TAP controller is a finite state machine that uses the state of the TMS ball at the
rising edge of TCK to navigate through its various modes of operation (see Figure 68
Test-Logic-Reset
The test-logic-reset controller state is entered when TMS is held HIGH for at least five
consecutive rising edges of TCK. As long as TMS remains HIGH, the TAP controller will
remain in the test-logic-reset state. The test logic is inactive during this state.
Run-Test/Idle
The run-test/idle is a controller state in between scan operations. This state can be
maintained by holding TMS LOW. From there, either the data register scan, or subse-
quently, the instruction register scan, can be selected.
Select-DR-Scan
Select-DR-scan is a temporary controller state. All test data registers retain their previ-
ous state while here.
Capture-DR
The capture-DR state is where the data is parallel-loaded into the test data registers. If
the boundary-scan register is the currently selected register, then the data currently on
the balls is latched into the test data registers.
Shift-DR
Data is shifted serially through the data register while in this state. As new data is input
through the TDI ball, data is shifted out of the TDO ball.
Exit1-DR, Pause-DR, and Exit2-DR
The purpose of exit1-DR is used to provide a path to return back to the run-test/idle
state (through the update-DR state). The pause-DR state is entered when the shifting of
data through the test registers needs to be suspended. When shifting is to reconvene,
the controller enters the exit2-DR state and then can re-enter the shift-DR state.
Update-DR
When the EXTEST instruction is selected, there are latched parallel outputs of the boun-
dary-scan shift register that only change state during the update-DR controller state.
Instruction Register States
The instruction register states of the TAP controller are similar to the data register
states. The desired instruction is serially shifted into the instruction register during the
shift-IR state and is loaded during the update-IR state.
PDF: 09005aef84003617
576mb_rldram3.pdf – Rev. B 1/12 EN
103
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