DS21448A1 Maxim Integrated, DS21448A1 Datasheet - Page 45

• Manufacturer Part Number: DS21448A1
• Description: Network Controller & Processor ICs 3.3V E1/T1/J1 Quad Interface
• Manufacturer: Maxim Integrated

Specifications of DS21448A1

• Part # Aliases: 90-21448-0A1

Select-IR-Scan. All test registers retain their previous state. The instruction register remains unchanged during this
state. With JTMS LOW, a rising edge on JTCLK moves the controller into the capture-IR state and initiates a scan
sequence for the instruction register. JTMS HIGH during a rising edge on JTCLK puts the controller back into the
test-logic-reset state.
Capture-IR. The capture-IR state is used to load the shift register in the instruction register with a fixed value. This
value is loaded on the rising edge of JTCLK. If JTMS is HIGH on the rising edge of JTCLK, the controller enters the
exit1-IR state. If JTMS is LOW on the rising edge of JTCLK, the controller enters the shift-IR state.
Shift-IR. In this state, the shift register in the instruction register is connected between JTDI and JTDO and shifts
data one stage for every rising edge of JTCLK toward the serial output. The parallel register and all test registers
remain at their previous states. A rising edge on JTCLK with JTMS HIGH moves the controller to the exit1-IR state.
A rising edge on JTCLK with JTMS LOW keeps the controller in the shift-IR state while moving data one stage
through the instruction shift register.
Exit1-IR. A rising edge on JTCLK with JTMS LOW puts the controller in the pause-IR state. If JTMS is HIGH on the
rising edge of JTCLK, the controller enters the update-IR state and terminates the scanning process.
Pause-IR. Shifting of the instruction shift register is halted temporarily. With JTMS HIGH, a rising edge on JTCLK
puts the controller in the exit2-IR state. The controller remains in the pause-IR state if JTMS is LOW during a rising
edge on JTCLK.
Exit2-IR. A rising edge on JTCLK with JTMS HIGH puts the controller in the update-IR state. The controller loops
back to shift-IR if JTMS is LOW during a rising edge of JTCLK in this state.
Update-IR. The instruction code shifted into the instruction shift register is latched into the parallel output on the
falling edge of JTCLK as the controller enters this state. Once latched, this instruction becomes the current
instruction. A rising edge on JTCLK with JTMS LOW puts the controller in the run-test-idle state. With JTMS HIGH,
the controller enters the select-DR-scan state.
8.2 Instruction Register
The instruction register contains a shift register, as well as a latched parallel output, and is 3 bits in length. When
the TAP controller enters the shift-IR state, the instruction shift register is connected between JTDI and JTDO.
While in the shift-IR state, a rising edge on JTCLK with JTMS LOW shifts the data one stage toward the serial
output at JTDO. A rising edge on JTCLK in the exit1-IR state or the exit2-IR state with JTMS HIGH moves the
controller to the update-IR state. The falling edge of that same JTCLK latches the data in the instruction shift
register to the instruction parallel output.
respective operational binary codes.
Table 8-A. Instruction Codes for IEEE 1149.1 Architecture
SAMPLE/PRELOAD. This is a mandatory instruction for the IEEE 1149.1 specification that supports two functions.
The digital I/Os of the device can be sampled at the boundary scan register without interfering with the normal
operation of the device by using the capture-DR state. SAMPLE/PRELOAD also allows the device to shift data into
the boundary scan register through JTDI using the shift-DR state.
BYPASS. When the BYPASS instruction is latched into the parallel instruction register, JTDI connects to JTDO
through the 1-bit bypass test register. This allows data to pass from JTDI to JTDO without affecting the device’s
normal operation.
SAMPLE/PRELOAD
INSTRUCTION
BYPASS
EXTEST
IDCODE
CLAMP
HIGHZ
SELECTED REGISTER
Device Identification
Boundary Scan
Boundary Scan
Bypass
Bypass
Bypass
Table 8-A
45 of 60
shows the instructions supported by the DS21448 and its
INSTRUCTION CODES
010
111
000
011
100
001