CY7C1471V33
CY7C1473V33
CY7C1475V33
Document #: 38-05288 Rev. *J
Page 15 of 32
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 time (t
CS
plus 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 CLK 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 balls.
Note that since the PRELOAD part of the command is not
implemented, putting the TAP to the Update-DR state while
performing a SAMPLE/PRELOAD instruction has 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 balls. 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.
TAP Timing
t
TL
Test Clock
(TCK )
1
2
3
4
5
6
Test M ode Select
(TM S)
tTH
Test Data-O ut
(TDO )
tCYC
Test Data-In
(TDI)
tTM SH
tTM SS
tTDIH
tTDIS
tTDOX
tTDOV
DO N’T CA RE
UNDEFINED
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