14
INDUSTRIAL TEMPERATURE RANGE
IDT72V71660 3.3V TIME SLOT INTERCHANGE
DIGITAL SWITCH 16,384 x 16,384
JTAG SUPPORT
The IDT72V71660 JTAG interface conforms to the Boundary-Scan standard
IEEE-1149.1. This standard specifies a design-for-testability technique called
Boundary-Scan test (BST). The operation of the boundary-scan circuitry is
controlled by an external Test Access Port (TAP) Controller.
TEST ACCESS PORT (TAP)
The Test Access Port (TAP) provides access to the test functions of the
IDT72V71660. It consists of three input pins and one output pin.
•Test Clock Input (TCK)
TCK provides the clock for the test logic. The TCK does not interfere with any
on-chip clock and thus remains independent. The TCK permits shifting of test
data into or out of the Boundary-Scan register cells concurrently with the
operation of the device and without interfering with the on-chip logic.
•Test Mode Select Input (TMS)
The logic signals received at the TMS input are interpreted by the Test Access
Port Controller to control the test operations. The TMS signals are sampled at
the rising edge of the TCK pulse. This pin is internally pulled to VCC when it is
not driven from an external source.
•Test Data Input (TDI)
Serial input data applied to this port is fed either into the instruction register
or into a test data register, depending on the sequence previously applied to
the TMS input. Both registers are described in a subsequent section. The
received input data is sampled at the rising edge of TCK pulses. This pin is
internally pulled to VCC when it is not driven from an external source.
•Test Data Output (TDO)
Depending on the sequence previously applied to the TMS input, the contents
of either the instruction register or data register are serially shifted out through
the TDO pin on the falling edge of each TCK pulse. When no data is shifted
through the boundary scan cells, the TDO driver is set to a high-impedance state.
•Test Reset (TRST)
Reset the JTAG scan structure. This pin is internally pulled to VCC when it
is not driven from an external source.
INSTRUCTION REGISTER
In accordance with the IEEE-1149.1 standard, the IDT72V71660 uses public
instructions. The IDT72V71660 JTAG interface contains a four-bit instruction
register. Instructions are serially loaded into the instruction register from the TDI
when the Test Access Port Controller is in its shift-IR state. Subsequently, the
instructions are decoded to achieve two basic functions: to select the test data
register that may operate while the instruction is current, and to define the serial
test data register path, which is used to shift data between TDI and TDO during
data register scanning. See Table 12 below for Instruction decoding.
TEST DATA REGISTER
As specified in IEEE-1149.1, the IDT72V71660 JTAG Interface contains two
test data registers:
•The Boundary-Scan register
The Boundary-Scan register consists of a series of Boundary-Scan cells
arranged to form a scan path around the boundary of the IDT72V71660 core
logic.
•The Bypass Register
The Bypass register is a single stage shift register that provides a one-bit path
from TDI to TDO. The IDT72V71660 boundary scan register bits are shown
in Table 14. Bit 0 is the first bit clocked out. All three-state enable bits are active
HIGH.
ID CODE REGISTER
As specified in IEEE-1149.1, this instruction loads the IDR with the Revision
Number, Device ID, and ID Register Indicator Bit. See Table 10.
INSTRUCTION FIELD VALUE DESCRIPTION
Revision Number (31:28) 0x0 Reserved for version number
IDT Device ID (27:12) 0x434 Defines IDT part number
IDT JEDEC ID (11:1) 0x33 Allows unique identification of device vendor as IDT
ID Register Indicator Bit (Bit 0) 1 Indicates the presence of an ID register
TABLE 10 — IDENTIFICATION REGISTER DEFINITIONS
REGISTER NAME BIT SIZE
Instruction (IR) 4
Bypass (BYR) 1
Identification (IDR) 32
Boundary Scan (BSR) Note(1)
TABLE 11 — SCAN REGISTER SIZES
NOTE:
1. The Boundary Scan Descriptive Language (BSDL) file for this device is available on
the IDT website (www.idt.com), or by contacting your local IDT sales representative.
