Tap controller state diagram – Cypress CY7C1446AV33 User Manual
Page 11
CY7C1440AV33
CY7C1442AV33
CY7C1446AV33
Document #: 38-05383 Rev. *E
Page 11 of 31
IEEE 1149.1 Serial Boundary Scan (JTAG)
The CY7C1440AV33/CY7C1442AV33/CY7C1446AV33 incor-
porates a serial boundary scan test access port (TAP). This
part is fully compliant with IEEE Standard 1149.1. The TAP
operates using JEDEC-standard 3.3V or 2.5V I/O logic levels.
The CY7C1440AV33/CY7C1442AV33/CY7C1446AV33 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 should be
left unconnected. Upon power-up, the device will come up in
a reset state which will not interfere with the operation of the
device.
TAP Controller State Diagram
The 0/1 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. It is allowable to
leave this ball 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 application. TDI is connected to the most signif-
icant 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
Truth Table for Read/Write
[4, 8, 9]
Function (CY7C1446AV33)
GW
BWE
BW
X
Read
H
H
X
Read
H
L
All BW = H
Write Byte x – (DQ
x
and DQP
x
)
H
L
L
Write All Bytes
H
L
All BW = L
Write All Bytes
L
X
X
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