GS8162Z18(B/D)/GS8162Z36(B/D)/GS8162Z72(C)
JTAG Tap Controller State Diagram
Test Logic Reset
1
0
1
1
1
Run Test Idle
Select DR
Select IR
0
0
0
1
1
1
1
Capture DR
Capture IR
0
0
Shift DR
Shift IR
0
0
1
1
Exit1 DR
Exit1 IR
0
0
Pause DR
Pause IR
0
0
0
0
1
1
Exit2 DR
Exit2 IR
1
1
Update DR
Update IR
1
0
1
0
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 facili-
tate 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 Instruction 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. The EXTEST command does not block or override the RAM’s input pins; therefore, the RAM’s internal state is
still determined by its input pins.
Rev: 2.21 11/2004
27/38
© 1999, GSI Technology
Specifications cited are subject to change without notice. For latest documentation see http://www.gsitechnology.com.
GSI [ GSI TECHNOLOGY ]
