Maxim Integrated DS4830 Optical Microcontroller - Manual (Page 150)

DS4830 User’s Guide
150
20.1 – TAP Controller
The TAP controller is a synchronous state machine that responds to changes at the TMS and TCK signals. Based on its
state transition, the controller provides the clock and control sequence for TAP operation. The performance of the TAP is
dependent on the TCK clock frequency. The maximum TCK clock frequency should be limited to 1/8 the system clock
frequency. This section provides a brief description of the state machine and its state transitions. The state diagram in
Figure 20-1 summarizes the transitions caused by the TMS signal sampling on the rising edge at TCK. The TMS signal
value is presented adjacent to each state transition in the figure.
TEST-LOGIC-RESET
RUN-TEST-IDLE SELECT-DR-SCAN
EXIT2-DR
CAPTURE-DR
SHIFT-DR
EXIT1-DR
PAUSE-DR
UPDATE-DR
SELECT-IR-SCAN
EXIT2-IR
CAPTURE-IR
SHIFT-IR
EXIT1-IR
PAUSE-IR
UPDATE-IR
1
0
1 1 1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0 0
1 1
0 0
Figure 20-2: TAP Controller State Diagram