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

25/35

© 2011, GSI Technology

Boundary Scan Register

The Boundary Scan Register is a collection of flip flops that can be preset by the logic level found on the RAM’s input or I/O pins.

The flip flops are then daisy chained together so the levels found can be shifted serially out of the JTAG Port’s TDO pin. The

Boundary Scan Register also includes a number of place holder flip flops (always set to a logic 1). The relationship between the

device pins and the bits in the Boundary Scan Register is described in the Scan Order Table following. The Boundary Scan

Register, under the control of the TAP Controller, is loaded with the contents of the RAMs I/O ring when the controller is in

Capture-DR state and then is placed between the TDI and TDO pins when the controller is moved to Shift-DR state. SAMPLE-Z,

SAMPLE/PRELOAD and EXTEST instructions can be used to activate the Boundary Scan Register.

Instruction Register

ID Code Register

Boundary Scan Register

0

1

2

0

·· · ·

31 30 29

1

2

0

Bypass Register

TDI

TDO

TMS

TCK

Test Access Port (TAP) Controller

·

·

·

·

·

···

·

·

Control Signals

·

JTAG TAP Block Diagram

Identification (ID) Register

The ID Register is a 32-bit register that is loaded with a device and vendor specific 32-bit code when the controller is put in

Capture-DR state with the IDCODE command loaded in the Instruction Register. The code is loaded from a 32-bit on-chip ROM.

It describes various attributes of the RAM as indicated below. The register is then placed between the TDI and TDO pins when the

controller is moved into Shift-DR state. Bit 0 in the register is the LSB and the first to reach TDO when shifting begins.