Advance
576Mb: x18, x36 RLDRAM 3
IEEE 1149.1 Serial Boundary Scan (JTAG)
TAP Instruction Set
Overview
There are 28 different instructions possible with the 8-bit instruction register. All combi-
nations used are listed in Table 47 (page 110). These six instructions are described in
detail below. The remaining instructions are reserved and should not be used.
The TAP controller used in this RLDRAM 3 device is fully compliant to the IEEE 1149.1
convention.
Instructions are loaded into the TAP controller during the shift-IR state when the in-
struction register is placed between TDI and TDO. During this state, instructions are
shifted through the instruction register through the TDI and TDO balls. To execute the
instruction after it is shifted in, the TAP controller needs to be moved into the update-IR
state.
EXTEST
The EXTEST instruction enables circuitry external to the component package to be tes-
ted. Boundary-scan register cells at output balls are used to apply a test vector, while
those at input balls capture test results. Typically, the first test vector to be applied using
the EXTEST instruction will be shifted into the boundary-scan register using the PRE-
LOAD instruction. Thus, during the update-IR state of EXTEST, the output driver is
turned on, and the PRELOAD data is driven onto the output balls.
IDCODE
The IDCODE instruction causes a vendor-specific, 32-bit code to be loaded into the in-
struction register. It also places the instruction register between the TDI and TDO balls
and enables the IDCODE to be shifted out of the device when the TAP controller enters
the shift-DR state. The IDCODE instruction is loaded into the instruction register upon
power-up or whenever the TAP controller is given a test logic reset state.
High-Z
The High-Z instruction causes the bypass register to be connected between the TDI and
TDO. This places all RLDRAM outputs into a High-Z state.
CLAMP
When the CLAMP instruction is loaded into the instruction register, the data driven by
the output balls are determined from the values held in the boundary-scan register.
SAMPLE/PRELOAD
When the SAMPLE/PRELOAD instruction is loaded into the instruction register and the
TAP controller is in the capture-DR state, a snapshot can be taken of the states of the
component's input and output signals without interfering with the normal operation of
the assembled board. The snapshot is taken on the rising edge of TCK and is captured in
the boundry-scan register. The data can then be viewed by shifting through the compo-
nent's TDO output.
The user must be aware that the TAP controller clock can only operate at a frequency up
to 50 MHz, while the RLDRAM 3 clock operates significantly faster. Because there is a
large difference between the clock frequencies, it is possible that during the capture-DR
state, an input or output will undergo a transition. The TAP may then try to capture a
signal while in transition (metastable state). This will not harm the device, but there is
PDF: 09005aef84003617
576mb_rldram3.pdf – Rev. B 1/12 EN
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