27
COMMERCIAL AND INDUSTRIAL
TEMPERATURE RANGES
IDT72T2098/108/118/128 2.5V HIGH-SPEED TeraSync™ DDR/SDR FIFO 20-BIT/10-BIT CONFIGURATIONS
32K x 20/64K x 10, 64K x 20/128K x 10, 128K x 20/256K x 10, 256K x 20/512K x 10
FEBRUARY 13, 2009
THE INSTRUCTION REGISTER
The Instruction register allows an instruction to be shifted in serially into the
processor at the rising edge of TCLK.
The Instruction is used to select the test to be performed, or the test data
register to be accessed, or both. The instruction shifted into the register is latched
at the completion of the shifting process when the TAP controller is at Update-
IR state.
The instruction register must contain 4 bit instruction register-based cells
which can hold instruction data. These mandatory cells are located nearest the
serial outputs they are the least significant bits.
TEST DATA REGISTER
The Test Data register contains three test data registers: the Bypass, the
Boundary Scan register and Device ID register.
These registers are connected in parallel between a common serial input
and a common serial data output.
The following sections provide a brief description of each element. For a
complete description, refer to the IEEE Standard Test Access Port Specification
(IEEE Std. 1149.1-1990).
TEST BYPASS REGISTER
The register is used to allow test data to flow through the device from TDI
to TDO. It contains a single stage shift register for a minimum length in serial path.
When the bypass register is selected by an instruction, the shift register stage
is set to a logic zero on the rising edge of TCLK when the TAP controller is in
the Capture-DR state.
The operation of the bypass register should not have any effect on the
operation of the device in response to the BYPASS instruction.
THE BOUNDARY-SCAN REGISTER
The Boundary Scan Register allows serial data TDI be loaded in to or read
out of the processor input/output ports. The Boundary Scan Register is a part
of the IEEE 1149.1-1990 Standard JTAG Implementation.
THE DEVICE IDENTIFICATION REGISTER
The Device Identification Register is a Read Only 32-bit register used to
specify the manufacturer, part number and version of the processor to be
determined through the TAP in response to the IDCODE instruction.
IDT JEDEC ID number is 0xB3. This translates to 0x33 when the parity
is dropped in the 11-bit Manufacturer ID field.
For the IDT72T2098/72T20108/72T20118/72T20128, the Part Number
field contains the following values:
IDT72T2098/108/118/128 JTAG Device Identification Register
31(MSB) 28 27 12 11 1 0(LSB)
Version (4 bits) Part Number (16-bit) Manufacturer ID (11-bit)
0X0 0X33 1
JTAG INSTRUCTION REGISTER
The Instruction register allows instruction to be serially input into the device
when the TAP controller is in the Shift-IR state. The instruction is decoded to
perform the following:
• Select test data registers that may operate while the instruction is
current. The other test data registers should not interfere with chip
operation and the selected data register.
• Define the serial test data register path that is used to shift data between
TDI and TDO during data register scanning.
The Instruction Register is a 4 bit field (i.e.IR3, IR2, IR1, IR0) to decode 16
different possible instructions. Instructions are decoded as follows.
Hex Instruction Function
Value
0x02 IDCODE Select Chip Identification data register
0x01 SAMPLE/PRELOAD Select Boundary Scan Register
0x03 HI-IMPEDANCE JTAG
0x0F BYPASS Select Bypass Register
Table 8. JTAG Instruction Register Decoding
The following sections provide a brief description of each instruction. For
a complete description refer to the IEEE Standard Test Access Port Specification
(IEEE Std. 1149.1-1990).
IDCODE
The optional IDCODE instruction allows the IC to remain in its functional mode
and selects the optional device identification register to be connected between
TDI and TDO. The device identification register is a 32-bit shift register containing
information regarding the IC manufacturer, device type, and version code.
Accessing the device identification register does not interfere with the operation
of the IC. Also, access to the device identification register should be immediately
available, via a TAP data-scan operation, after power-up of the IC or after the
TAP has been reset using the optional TRST pin or by otherwise moving to the
Test-Logic-Reset state.
SAMPLE/PRELOAD
The required SAMPLE/PRELOAD instruction allows the IC to remain in a
normal functional mode and selects the boundary-scan register to be connected
between TDI and TDO. During this instruction, the boundary-scan register can
be accessed via a date scan operation, to take a sample of the functional data
entering and leaving the IC.
HIGH-IMPEDANCE
The optional High-Impedance instruction sets all outputs (including two-state
as well as three-state types) of an IC to a disabled (high-impedance) state and
selects the one-bit bypass register to be connected between TDI and TDO.
During this instruction, data can be shifted through the bypass register from TDI
to TDO without affecting the condition of the IC outputs.
BYPASS
The required BYPASS instruction allows the IC to remain in a normal
functional mode and selects the one-bit bypass register to be connected
between TDI and TDO. The BYPASS instruction allows serial data to be
transferred through the IC from TDI to TDO without affecting the operation of
the IC.
EXTEST
The required EXTEST instruction is not available for this device.
Device Part# Field
IDT72T2098 04AB
IDT72T20108 04AA
IDT72T20118 04A9
IDT72T20128 04A8
