IDT82P2288
OCTAL T1/E1/J1 LONG HAUL / SHORT HAUL TRANSCEIVER
IEEE STD 1149.1 JTAG Test Access Port
343
March 04, 2009
6.3
TEST ACCESS PORT CONTROLLER
The TAP controller is a 16-state synchronous state machine.
Figure -42 shows its state diagram. A description of each state is listed in
Table 85. Note that the figure contains two main branches to access
either the data or instruction registers. The value shown next to each
state transition in this figure states the value present at TMS at each
rising edge of TCK.
D2_OUT
24
OUT-CELL
D2_IN
23
IN-CELL
D3_OUT
22
OUT-CELL
D3_IN
21
IN-CELL
D4_OUT
20
OUT-CELL
D4_IN
19
IN-CELL
D5_OUT
18
OUT-CELL
D5_IN
17
IN-CELL
D6_OUT
16
OUT-CELL
D6_IN
15
IN-CELL
D7_OUT
14
OUT-CELL
D7_IN
13
IN-CELL
D_OEN
12
OUT-CELL
A[0]
11
IN-CELL
A[1]
10
IN-CELL
Table 84: Boundary Scan (BS) Sequence (Continued)
BS-Cell Name
BS No.
BS-Cell Type
A[2]
9
IN-CELL
A[3]
8
IN-CELL
A[4]
7
IN-CELL
A[5]
6
IN-CELL
A[6]
5
IN-CELL
A[7]
4
IN-CELL
A[8]
3
IN-CELL
A[9]
2
IN-CELL
A[10]
1
IN-CELL
Table 84: Boundary Scan (BS) Sequence (Continued)
BS-Cell Name
BS No.
BS-Cell Type
Table 85: TAP Controller State Description
State
Description
Test Logic
Reset
In this state, the test logic is disabled to continue normal operation of the device. During initialization, the device initializes the instruction register with
the IDCODE instruction.
Regardless of the original state of the controller, the controller enters the Test-Logic-Reset state when the TMS input is held high for at least 5 rising
edges of TCK. The controller remains in this state while TMS is high.
Run-Test/
Idle
This is a controller state between scan operations. Once in this state, the controller remains in the state as long as TMS is held low. The instruction reg-
ister and all test data registers retain their previous state. When TMS is high and a rising edge is applied to TCK, the controller moves to the Select-DR
state.
Select-
DR-Scan
This is a temporary controller state and the instruction does not change in this state. The test data register selected by the current instruction retains its
previous state. If TMS is held low and a rising edge is applied to TCK when in this state, the controller moves into the Capture-DR state and a scan
sequence for the selected test data register is initiated. If TMS is held high and a rising edge applied to TCK, the controller moves to the Select-IR-Scan
state.
Capture-
DR
In this state, the Boundary Scan Register captures input pin data if the current instruction is EXTEST or SAMPLE/PRELOAD. The instruction does not
change in this state. The other test data registers, which do not have parallel input, are not changed. When the TAP controller is in this state and a ris-
ing edge is applied to TCK, the controller enters the Exit1-DR state if TMS is high or the Shift-DR state if TMS is low.
Shift-DR
In this controller state, the test data register connected between TDI and TDO as a result of the current instruction shifts data on stage toward its serial
output on each rising edge of TCK. The instruction does not change in this state. When the TAP controller is in this state and a rising edge is applied to
TCK, the controller enters the Exit1-DR state if TMS is high or remains in the Shift-DR state if TMS is low.
Exit1-DR This is a temporary state. While in this state, if TMS is held high, a rising edge applied to TCK causes the controller to enter the Update-DR state, which
terminates the scanning process. If TMS is held low and a rising edge is applied to TCK, the controller enters the Pause-DR state. The test data register
selected by the current instruction retains its previous value and the instruction does not change during this state.