IS61VPD51236A Datasheet, PDF (19/29 Pages) Integrated Silicon Solution, Inc – 512K x 36, 1024K x 18 18Mb SYNCHRONOUS PIPELINED, DOUBLE CYCLE DESELECT STATIC RAM

IS61VPD51236A, IS61VPD102418A, IS61LPD51236A, IS61LPD102418A
ISSI ^®
TEST DATA OUT (TDO)
The TDO output pin is used to serially clock data-out from
the registers. The output is active depending on the
current state of the TAP state machine (see TAP Controller
State Diagram). The output changes on the falling edge of
TCK and TDO is connected to the Least Significant Bit
(LSB) of any register.
PERFORMING A TAP RESET
A Reset is performed by forcing TMS HIGH (VDD) for five
rising edges of TCK. RESET may be performed while the
SRAM is operating and does not affect its operation. At
power-up, the TAP is internally reset to ensure that TDO
comes up in a high-Z state.
TAP REGISTERS
Registers are connected between the TDI and TDO pins
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 registers. Data is serially loaded
into the TDI pin on the rising edge of TCK and output on the
TDO pin 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 pins. (See TAP Controller
Block Diagram) At 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 previously described.
When the TAP controller is in the CaptureIR state, the two
least significant bits are loaded with a binary “01” pattern
to allow for fault isolation of the board level serial test path.
Bypass Register
To save time when serially shifting data through registers,
it is sometimes advantageous to skip certain states. The
bypass register is a single-bit register that can be placed
between TDI and TDO pins. This allows data to be shifted
through the SRAM with minimal delay. The bypass register
is set LOW (Vss) when the BYPASS instruction is ex-
ecuted.
Boundary Scan Register
The boundary scan register is connected to all input and
output pins on the SRAM. Several no connect (NC) pins are
also included in the scan register to reserve pins for higher
density devices. The x36 configuration has a 75-bit-long
register and the x18 configuration also has a 75-bit-long
register. The boundary scan register is loaded with the
contents of the RAM Input and Output ring when the TAP
controller is in the Capture-DR state and then placed
between the TDI and TDO pins 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 Input and Output ring.
The Boundary Scan Order tables show the order in which the
bits are connected. Each bit corresponds to one of the
bumps on the SRAM package. The MSB of the register is
connected to TDI, and the LSB is connected to TDO.
Scan Register Sizes
Register Name
Instruction
Bypass
ID
Boundary Scan
Bit Size (x18)
3
1
32
75
Bit Size (x36)
3
1
32
75
Identification (ID) Register
The ID register is loaded with a vendor-specific, 32-bit
code during the Capture-DR state when the IDCODE
command is loaded to the instruction register. 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 vendor code and other information described in the
Identification Register Definitions table.
IDENTIFICATION REGISTER DEFINITIONS
Instruction Field
Revision Number (31:28)
Device Depth (27:23)
Device Width (22:18)
ISSI Device ID (17:12)
ISSI JEDEC ID (11:1)
ID Register Presence (0)
Description
Reserved for version number.
Defines depth of SRAM. 512K or 1M
Defines with of the SRAM. x36 or x18
Reserved for future use.
Allows unique identification of SRAM vendor.
Indicate the presence of an ID register.
512K x 36
xxxx
00111
00100
xxxxx
00011010101
1
1M x 18
xxxx
01000
00011
xxxxx
00011010101
1
Integrated Silicon Solution, Inc. — 1-800-379-4774
19
Rev. B
02/03/06