CY7C1370C Datasheet, PDF (11/27 Pages) Cypress Semiconductor – 512K x 36/1M x 18 Pipelined SRAM with NoBL Architecture

CY7C1370C
CY7C1372C
the SRAM and cannot preload the Input or Output buffers. The
SRAM does not implement the 1149.1 commands EXTEST or
INTEST or the PRELOAD portion of SAMPLE/PRELOAD;
rather it performs a capture of the Inputs and Output ring when
these instructions are executed.
Instructions are loaded into the TAP controller during the
Shift-IR state when the instruction register is placed between
TDI and TDO. During this state, instructions are shifted
through the instruction register through the TDI and TDO pins.
To execute the instruction once it is shifted in, the TAP
controller needs to be moved into the Update-IR state.
EXTEST
EXTEST is a mandatory 1149.1 instruction which is to be
executed whenever the instruction register is loaded with all
0s. EXTEST is not implemented in the TAP controller, and
therefore this device is not compliant to the 1149.1 standard.
The TAP controller does recognize an all-0 instruction. When
an EXTEST instruction is loaded into the instruction register,
the SRAM responds as if a SAMPLE/PRELOAD instruction
has been loaded. There is one difference between the two
instructions. Unlike the SAMPLE/PRELOAD instruction,
EXTEST places the SRAM outputs in a High-Z state.
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 pins 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.
SAMPLE Z
The SAMPLE Z instruction causes the boundary scan register
to be connected between the TDI and TDO pins when the TAP
controller is in a Shift-DR state. It also places all SRAM outputs
into a High-Z state.
SAMPLE/PRELOAD
SAMPLE/PRELOAD is a 1149.1 mandatory instruction. The
PRELOAD portion of this instruction is not implemented, so
the TAP controller is not fully 1149.1-compliant.
When the SAMPLE/PRELOAD instructions are loaded into the
instruction register and the TAP controller is in the Capture-DR
state, a snapshot of data on the inputs and output pins 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 more than an order of magnitude faster. Because
there is a large difference in 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 no guarantee as to the value that will
be captured. Repeatable results may not be possible.
To guarantee 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 set-up plus
hold times (t_CS and t_CH). 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 CK and CK# 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 pins.
Note that since the PRELOAD part of the command is not
implemented, putting the TAP into the Update to the
Update-DR state while performing a SAMPLE/PRELOAD
instruction will have the same effect as the Pause-DR
command.
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 the TDI and TDO pins. The
advantage of the BYPASS instruction is that it shortens the
boundary scan path when multiple devices are connected
together on a board.
Reserved
These instructions are not implemented but are reserved for
future use. Do not use these instructions.
Document #: 38-05233 Rev. *D
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