CY7C1354DV25
CY7C1356DV25
Document #: 001-48974 Rev. *A
Page 10 of 29
IEEE 1149.1 Serial Boundary Scan (JTAG)
The CY7C1354DV25 and CY7C1356DV25 incorporates a serial
boundary scan test access port (TAP) in the BGA package only.
The TQFP package does not offer this functionality. This part
operates in accordance with IEEE Standard 1149.1-1900, but
does not have the set of functions required for full 1149.1
compliance. These functions from the IEEE specification are
excluded because their inclusion places an added delay in the
critical speed path of the SRAM. Note the TAP controller
functions in a manner that does not conflict with the operation of
other devices using 1149.1 fully compliant TAPs. The TAP
operates using JEDEC-standard 2.5V I/O logic levels.
The CY7C1354DV25 and CY7C1356DV25 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
(VSS) to prevent clocking of the device. TDI and TMS are inter-
nally pulled up and may be unconnected. They may alternately
be connected to VDD through a pull-up resistor. TDO should be
left unconnected. During power up, the device comes up in a
reset state which does not interfere with the operation of the
device.
Write cycle description for CY7C1356DV25 follows.
[1, 2, 3, 8]
Function
WE
BWb
BWa
Read
Hx
x
Write – No Bytes Written
L
H
H
Write Byte a
− (DQ
a and DQPa)
LHL
Write Byte b – (DQb and DQPb)
LL
H
Write Both Bytes
L
L
L
Notes
8. Table only lists a partial listing of the byte write combinations. Any combination of BWX is valid. Appropriate write will be done based on which byte write is active.
9. The 0/1 next to each state represents the value of TMS at the rising edge of the TCK.
Figure 1. TAP Controller State Diagram[9]
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
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