IS61LPS51236B Datasheet, PDF (21/33 Pages) Integrated Silicon Solution, Inc – Internal self-timed write cycle

IS61LPS51236B/IS61VPS51236B/IS61VVPS51236B
IS61LPS102418B/IS61VPS102418B/IS61VVPS102418B
1. EXTEST
The EXTEST instruction allows circuitry external to the component package to be tested. 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
PRELOAD 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.
2. IDCODE
The IDCODE instruction causes a vendor-specific, 32-bit code to be loaded into the instruction register. It also
places the instruction register between the TDI and TDO balls and allows 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.
3. SAMPLE Z
If the SAMPLE-Z instruction is loaded in the instruction register, all SRAM outputs are forced to an inactive drive
state (high-Z), moving the TAP controller into the capture-DR state loads the data in the SRAMs input into the
boundary scan register, and the boundary scan register is connected between TDI and TDO when the TAP
controller is moved to the shift-DR state.
4. 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 of data on the inputs and bidirectional balls is captured in the boundary scan register.
The user must be aware that the TAP controller clock can only operate at a frequency up to 10 MHz, while the
SRAM 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. This will not harm the device, but there is no guarantee as to the value that will
be captured. Repeatable results may not be possible. To ensure that the boundary scan register will capture the
correct value of a signal, the SRAM signal must be stabilized long enough to meet the TAP controller’s capture
setup plus hold time. The SRAM clock input might not be captured correctly if there is no way in a design to stop
(or slow) the clock during a SAMPLE/ PRELOAD instruction. If this is an issue, it is still possible to capture all other
signals and simply ignore the value of the CLK captured in the boundary scan register. Once the data is captured,
it is possible to shift out the data by putting the TAP into the shift-DR state. This places the boundary scan register
between the TDI and TDO balls.
6. BYPASS
When the BYPASS instruction is loaded in the instruction register and the TAP is placed in a shift-DR state, the
bypass register is placed between TDI and TDO. The advantage of the BYPASS instruction is that it shortens the
boundary scan path when multiple devices are connected together on a board.
7. RESERVED
These instructions are not implemented but are reserved for future use. Please do not use these instructions.
Integrated Silicon Solution, Inc.- www.issi.com
21
Rev. B
10/16/2014