![](http://datasheet.mmic.net.cn/200000/GS8324Z18B-166IT_datasheet_15066747/GS8324Z18B-166IT_36.png)
Rev: 1.00 10/2001
36/46
2001, Giga Semiconductor, Inc.
Specifications cited are subject to change without notice. For latest documentation see http://www.gsitechnology.com.
Preliminary
GS8324Z18(B/C)/GS8324Z36(B/C)/GS8324Z72(C)
JTAG Tap Controller State Diagram
Instruction Descriptions
BYPASS
When the BYPASS instruction is loaded in the Instruction Register the Bypass Register is placed between TDI and TDO. This occurs when
the TAP controller is moved to the Shift-DR state. This allows the board level scan path to be shortened to facilitate testing of other devices
in the scan path.
SAMPLE/PRELOAD
SAMPLE/PRELOAD is a Standard 1149.1 mandatory public instruction. When the SAMPLE / PRELOAD instruction is loaded in the Instruc-
tion Register, moving the TAP controller into the Capture-DR state loads the data in the RAMs input and I/O buffers into the Boundary Scan
Register. Boundary Scan Register locations are not associated with an input or I/O pin, and are loaded with the default state identified in the
Boundary Scan Chain table at the end of this section of the datasheet. Because the RAM clock is independent from the TAP Clock (TCK) it
is possible for the TAP to attempt to capture the I/O ring contents while the input buffers are in transition (i.e. in a metastable state). Although
allowing the TAP to sample metastable inputs will not harm the device, repeatable results cannot be expected. RAM input signals must be
stabilized for long enough to meet the TAPs input data capture set-up plus hold time (tTS plus tTH). The RAMs clock inputs need not be
paused for any other TAP operation except capturing the I/O ring contents into the Boundary Scan Register. Moving the controller to Shift-
DR state then places the boundary scan register between the TDI and TDO pins.
EXTEST
EXTEST is an IEEE 1149.1 mandatory public instruction. It is to be executed whenever the instruction register is loaded with all logic 0s.
Select DR
Capture DR
Shift DR
Exit1 DR
Pause DR
Exit2 DR
Update DR
Select IR
Capture IR
Shift IR
Exit1 IR
Pause IR
Exit2 IR
Update IR
Test Logic Reset
Run Test Idle
0
1
0
1
0
1
0
1
0
1
0
1
0
1