Cypress Perform CY7C1380F - Manual (Page 12)

CY7C1380D, CY7C1382D
CY7C1380F, CY7C1382F
Document #: 38-05543 Rev. *F Page 12 of 34
IEEE 1149.1 Serial Boundary Scan (JTAG)
The CY7C1380D/CY7C1382D incorporates a serial boundary
scan test access port (TAP).This part is fully compliant with
1149.1. The TAP operates using JEDEC-standard 3.3V or 2.5V
I/O logic levels.
The CY7C1380D/CY7C1382D 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
(V
SS
) to prevent clocking of the device. TDI and TMS are inter-
nally pulled up and may be unconnected. They may alternately
be connected to V
DD
through a pull up resistor. TDO must be left
unconnected. Upon power up, the device comes up in a reset
state which does not interfere with the operation of the device.
TAP Controller State Diagram
The 0 or 1 next to each state represents the value of TMS at the
rising edge of TCK.
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. TDI is internally pulled
up and can be unconnected if the TAP is unused in an appli-
cation. TDI is connected to the most significant bit (MSB) of any
register. (See TAP Controller Block Diagram .)
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. The output changes on the falling edge
of TCK. TDO is connected to the least significant bit (LSB) of any
register. (See TAP Controller State Diagram .)
TAP Controller Block Diagram
Performing a TAP Reset
A Reset is performed by forcing TMS HIGH (V
DD
) 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.
TAP Registers
Registers are connected between the TDI and TDO balls and
enable data to be scanned in and out of the SRAM test circuitry.
Only one register can be selected at a time through the
instruction register. 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.
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.
TEST-LOGIC
RESET
RUN-TEST/
IDLE
SELECT
DR-SCAN
SELECT
IR-SCAN
CAPTURE-DR
SHIFT-DR
CAPTURE-IR
SHIFT-IR
EXIT1-DR
PAUSE-DR
EXIT1-IR
PAUSE-IR
EXIT2-DR
UPDATE-DR
EXIT2-IR
UPDATE-IR
1
1
1
0
1 1
0 0
1 1
1
0
0
0
0 0
0
0
0 0
1
0
1
1
0
1
0
1
1
1 1 0
Bypass Register
0
Instruction Register
0 1 2
Identification Register
0 1 2 29 30 31 . . .
Boundary Scan Register
0 1 2 . . x . . .
S election
Circuitr y
Selection
Circuitry
TCK
TMS TAP CONTROLLER
TDI TDO
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