GS8342T08/09/18/36BD-400/350/333/300/250

Specifications cited are subject to change without notice. For latest documentation see http://www.gsitechnology.com.

Rev: 1.02 6/2012

28/35

© 2011, GSI Technology

Typically, the Boundary Scan Register is loaded with the desired pattern of data with the SAMPLE/PRELOAD command.

Then the EXTEST command is used to output the Boundary Scan Register’s contents, in parallel, on the RAM’s data output

drivers on the falling edge of TCK when the controller is in the Update-IR state.

Alternately, the Boundary Scan Register may be loaded in parallel using the EXTEST command. When the EXTEST instruc-

tion is selected, the sate of all the RAM’s input and I/O pins, as well as the default values at Scan Register locations not asso-

ciated with a pin, are transferred in parallel into the Boundary Scan Register on the rising edge of TCK in the Capture-DR

state, the RAM’s output pins drive out the value of the Boundary Scan Register location with which each output pin is associ-

ated.

IDCODE

The IDCODE instruction causes the ID ROM to be loaded into the ID register when the controller is in Capture-DR mode and

places the ID register between the TDI and TDO pins in Shift-DR mode. The IDCODE instruction is the default instruction

loaded in at power up and any time the controller is placed in the Test-Logic-Reset state.

SAMPLE-Z

If the SAMPLE-Z instruction is loaded in the instruction register, all RAM outputs are forced to an inactive drive state (high-

Z) and the Boundary Scan Register is connected between TDI and TDO when the TAP controller is moved to the Shift-DR

state.

JTAG TAP Instruction Set Summary

Instruction

Code

Description

Notes

EXTEST

000

Places the Boundary Scan Register between TDI and TDO.

1

IDCODE

001

Preloads ID Register and places it between TDI and TDO.

1, 2

SAMPLE-Z

010

Captures I/O ring contents. Places the Boundary Scan Register between TDI and TDO.

Forces all RAM output drivers to High-Z.

1

GSI

011

GSI private instruction.

1

SAMPLE/PRELOAD

100

Captures I/O ring contents. Places the Boundary Scan Register between TDI and TDO.

1

GSI

101

GSI private instruction.

1

GSI

110

GSI private instruction.

1

BYPASS

111

Places Bypass Register between TDI and TDO.

1

Notes:

1. Instruction codes expressed in binary, MSB on left, LSB on right.

2. Default instruction automatically loaded at power-up and in test-logic-reset state.