Cypress CY7C1443AV33 Manual De Usuario
CY7C1441AV33
CY7C1443AV33,CY7C1447AV33
Document #: 38-05357 Rev. *G
Page 13 of 31
Instruction Register
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.
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.
register. This register is loaded when it is placed between the TDI
and TDO balls as shown in the Tap Controller Block Diagram.
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 data path.
significant bits are loaded with a binary “01” pattern to allow for
fault isolation of the board-level serial test data path.
Bypass Register
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 shifts data through the SRAM with
minimal delay. The bypass register is set LOW (V
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 shifts data through the SRAM with
minimal delay. The bypass register is set LOW (V
SS
) 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.
bidirectional balls on the SRAM.
The boundary scan register is loaded with the contents of the
RAM IO 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 IO ring.
RAM IO 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 IO ring.
The Boundary Scan Order tables 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.
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 the Identification Register Definitions
table.
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 the Identification Register Definitions
table.
TAP Instruction Set
Overview
Eight different instructions are possible with the three bit
instruction register. All combinations are listed in the Instruction
Codes table. Three of these instructions are listed as
RESERVED and should not be used. The other five instructions
are described in this section in detail.
instruction register. All combinations are listed in the Instruction
Codes table. Three of these instructions are listed as
RESERVED and should not be used. The other five instructions
are described in this section in detail.
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 balls. To execute
the instruction once it is shifted in, the TAP controller must be
moved into the Update-IR state.
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 balls. To execute
the instruction once it is shifted in, the TAP controller must be
moved into the Update-IR state.
IDCODE
The IDCODE instruction loads a vendor-specific, 32-bit code into
the instruction register. It also places the instruction register
between the TDI and TDO balls and shifts the IDCODE out of the
device when the TAP controller enters the Shift-DR state.
the instruction register. It also places the instruction register
between the TDI and TDO balls and shifts the IDCODE 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.
upon power up or whenever the TAP controller is given a test
logic reset state.
SAMPLE Z
The SAMPLE Z instruction connects the boundary scan register
between the TDI and TDO pins when the TAP controller is in a
Shift-DR state. The SAMPLE Z command puts the output bus
into a High-Z state until the next command is given during the
“Update IR” state.
between the TDI and TDO pins when the TAP controller is in a
Shift-DR state. The SAMPLE Z command puts the output bus
into a High-Z state until the next command is given during the
“Update IR” state.
SAMPLE/PRELOAD
SAMPLE/PRELOAD is a 1149.1 mandatory instruction. 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 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 20 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 undergoes a
transition. The TAP may then try to capture a signal while in
transition (metastable state). This does not harm the device, but
there is no guarantee as to the value that is captured.
Repeatable results may not be possible.
operate at a frequency up to 20 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 undergoes a
transition. The TAP may then try to capture a signal while in
transition (metastable state). This does not harm the device, but
there is no guarantee as to the value that is captured.
Repeatable results may not be possible.
To guarantee that the boundary scan register captures the
correct value of a signal, the SRAM signal must be stabilized
long enough to meet the TAP controller's capture setup plus hold
times (t
correct value of a signal, the SRAM signal must be stabilized
long enough to meet the TAP controller's capture setup 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.
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.
After 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.
putting the TAP into the Shift-DR state. This places the boundary
scan register between the TDI and TDO pins.
PRELOAD places an initial data pattern at the latched parallel
outputs of the boundary scan register cells prior to the selection
of another boundary scan test operation.
outputs of the boundary scan register cells prior to the selection
of another boundary scan test operation.
The shifting of data for the SAMPLE and PRELOAD phases can
occur concurrently when required—that is, while data captured
is shifted out, the preloaded data can be shifted in.
occur concurrently when required—that is, while data captured
is shifted out, the preloaded data can be shifted in.
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.
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.