MT54V1MH18E Micron Semiconductor Products, Inc., MT54V1MH18E Datasheet - Page 18

• Manufacturer Part Number: MT54V1MH18E
• Description: 18Mb QDR SRAM, 2.5V Vdd, Hstl, 4-Word Burst,
• Manufacturer: Micron Semiconductor Products, Inc.

illustrated in Figure 7. The output changes on the fall-
ing edge of TCK. TDO is connected to the least signifi
cant bit (LSB) of any register, as depicted in Figure 8.
Performing a TAP RESET
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.
that TDO comes up in a High-Z state.
TAP Registers
balls and allow data to be scanned into and out of the
SRAM test circuitry. Only one register can be selected
at a time through the instruction register. Data is seri-
ally 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
the instruction register. This register is loaded when it
is placed between the TDI and TDO balls, as shown in
Figure 8. 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.
the two LSBs are loaded with a binary “01” pattern to
allow for fault isolation of the board-level serial test
data path.
Bypass Register
isters, 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
allows data to be shifted through the SRAM with mini-
mal delay. The bypass register is set LOW (Vss) when
the BYPASS instruction is executed.
18Mb: 2.5V V
MT54V1MH18E_16_F.fm – Rev. F, Pub. 3/03
A RESET is performed by forcing TMS HIGH (V
At power-up, the TAP is reset internally to ensure
Registers are connected between the TDI and TDO
Three-bit instructions can be serially loaded into
When the TAP controller is in the Capture-IR state,
To save time when serially shifting data through reg-
DD
, HSTL, QDRb4 SRAM
DD
)
18
NOTE:
Boundary Scan Register
input and bidirectional balls on the SRAM. The SRAM
has a 107-bit-long register.
tents of the RAM I/O 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 I/O ring.
which the bits are connected. Each bit corresponds to
one of the balls on the SRAM package. The MSB of the
register is connected to TDI, and the LSB is connected
to TDO.
Identification (ID) Register
bit code during the Capture-DR state when the
IDCODE command is loaded in the instruction regis-
ter. 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.
TMS
TCK
TDI
X = 106.
The boundary scan register is connected to all the
The boundary scan register is loaded with the con-
The Boundary Scan Order tables show the order in
The ID register is loaded with a vendor-specific, 32-
2.5V V
Micron Technology, Inc., reserves the right to change products or specifications without notice.
TAP Controller Block Diagram
Selection
Circuitry
DD
TAP CONTROLLER
1 MEG x 18, 512K x 36
, HSTL, QDRb4 SRAM
Boundary Scan Register
31
Figure 8:
Identification Register
x
30
Instruction Register
.
29
.
Bypass Register
.
.
.
.
.
.
2
2
2
1
1
1
0
0
0
0
©2003 Micron Technology, Inc.
Selection
Circuitry
TDO