GS8321V18/32/36E-250/225/200/166/150/133

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

Rev: 1.03 4/2005

22/31

© 2003, GSI Technology

Tap Controller Instruction Set

Overview

There are two classes of instructions defined in the Standard 1149.1-1990; the standard (Public) instructions, and device specific

(Private) instructions. Some Public instructions are mandatory for 1149.1 compliance. Optional Public instructions must be

implemented in prescribed ways. The TAP on this device may be used to monitor all input and I/O pads, and can be used to load

address, data or control signals into the RAM or to preload the I/O buffers.

When the TAP controller is placed in Capture-IR state the two least significant bits of the instruction register are loaded with 01.

When the controller is moved to the Shift-IR state the Instruction Register is placed between TDI and TDO. In this state the desired

instruction is serially loaded through the TDI input (while the previous contents are shifted out at TDO). For all instructions, the

TAP executes newly loaded instructions only when the controller is moved to Update-IR state. The TAP instruction set for this

device is listed in the following table.

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

0

1

0

1

1

0

0

1

1

1

0

0

1

1

0

0

0

0

1

1

0

0

1

10

0

0

1

11

1

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 facili-

tate testing of other devices in the scan path.