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CY7C1381KV33 Datasheet(PDF) 13 Page - Cypress Semiconductor
CYPRESS [Cypress Semiconductor]
CY7C1381KV33 Datasheet(HTML) 13 Page - Cypress Semiconductor
/ 34 page
Document Number: 001-97888 Rev. *F
Page 13 of 34
IEEE 1149.1 Serial Boundary Scan (JTAG)
The CY7C1381KV33 incorporates a serial boundary scan test
access port (TAP). This part is fully compliant with 1149.1. The
TAP operates using JEDEC-standard 3.3 V or 2.5 V I/O logic
CY7C1381KV33 contains a TAP controller, instruction register,
boundary scan register, bypass register, and ID register.
Disabling the JTAG Feature
It is possible to operate the SRAM without using the JTAG
feature. To disable the TAP controller, TCK must be tied LOW
) to prevent clocking of the device. TDI and TMS are
internally pulled up and may be unconnected. They may
alternately be connected to V
through a pull-up resistor. TDO
may be left unconnected. At power up, the device comes up in a
reset state, which does not interfere with the operation of the
Test Access Port (TAP)
Test Clock (TCK)
The test clock is used only with the TAP controller. All inputs are
captured on the rising edge of TCK. All outputs are driven from
the falling edge of TCK.
Test Mode Select (TMS)
The TMS input is used to give commands to the TAP controller
and is sampled on the rising edge of TCK. This pin may be left
unconnected if the TAP is not used. The ball is pulled up
internally, resulting in a logic HIGH level.
Test Data-In (TDI)
The TDI ball is used to serially input information into the registers
and can be connected to the input of any of the registers. The
register between TDI and TDO is chosen by the instruction that
is loaded into the TAP instruction register. For information on
loading the instruction register, see the TAP Controller State
Diagram on page 15. TDI is internally pulled up and can be
unconnected if the TAP is unused in an application. TDI is
connected to the most significant bit (MSB) of any register.
Test Data-Out (TDO)
The TDO output ball is used to serially clock data-out from the
registers. The output is active depending upon the current state
of the TAP state machine (see Instruction Codes on page 19).
The output changes on the falling edge of TCK. TDO is
connected to the least significant bit (LSB) of any register.
Performing a TAP Reset
A reset is performed by forcing TMS HIGH (V
) for five rising
edges of TCK. This reset does not affect the operation of the
SRAM and may be performed while the SRAM is operating. At
power up, the TAP is reset internally to ensure that TDO comes
up in a high Z state.
Registers are connected between the TDI and TDO balls and
allow data to be scanned in and out of the SRAM test circuitry.
Only one register can be selected at a time through the
instruction registers. Data is serially loaded into the TDI ball on
the rising edge of TCK. Data is output on the TDO ball on the
falling edge of TCK.
Three-bit instructions can be serially loaded into the instruction
register. This register is loaded when it is placed between the TDI
and TDO balls as shown in the TAP Controller Block Diagram on
page 16. Upon power up, the instruction register is loaded with
the IDCODE instruction. It is also loaded with the IDCODE
instruction if the controller is placed in a reset state as described
in the previous section.
When the TAP controller is in the Capture-IR state, the two least
significant bits are loaded with a binary ‘01’ pattern to allow for
fault isolation of the board level serial test path.
To save time when serially shifting data through registers, it is
sometimes advantageous to skip certain chips. The bypass
register is a single-bit register that can be placed between the
TDI and TDO balls. This allows data to be shifted through the
SRAM with minimal delay. The bypass register is set LOW (V
when the BYPASS instruction is executed.
Boundary Scan Register
The boundary scan register is connected to all the input and
bidirectional balls on the SRAM.
The boundary scan register is loaded with the contents of the
RAM input and output ring when the TAP controller is in the
Capture-DR state and is then placed between the TDI and TDO
balls when the controller is moved to the Shift-DR state. The
EXTEST, SAMPLE/PRELOAD, and SAMPLE Z instructions can
be used to capture the contents of the input and output ring.
The Boundary Scan Order on page 20 show the order in which
the bits are connected. Each bit corresponds to one of the bumps
on the SRAM package. The MSB of the register is connected to
TDI, and the LSB is connected to TDO.
Identification (ID) Register
The ID register is loaded with a vendor-specific 32-bit code
during the Capture-DR state when the IDCODE command is
loaded in the instruction register. The IDCODE is hardwired into
the SRAM and can be shifted out when the TAP controller is in
the Shift-DR state. The ID register has a vendor code and other
information described in Identification Register Definitions on
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