AD6426 Analog Devices, AD6426 Datasheet - Page 27

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AD6426

Manufacturer Part Number
AD6426
Description
Enhanced GSM Processor
Manufacturer
Analog Devices
Datasheet

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TEST INTERFACE
The AD6426 provides a complete JTAG test interface. The
functionality of these pins are shown in Table 20.
Furthermore, these pins can assume a different functionality
described in detail in the chapter MODES OF OPERATION.
JTAG Port
The AD6426 provides full IEEE 1149.1 compliance. The
JTAG Port must be run at a frequency of 5 MHz or less.
The JTAG Port is explicitly enabled through JTAGEN. When
disabled, the corresponding pins are re-used for the AD6426
Feature Modes. The JTAG interface implements four registers
shown in Figure 10. The content of the Instruction register
selects one of these four registers.
The instruction register contains 4 bits, and supports the
instructions listed in Table 21.
Instruction register values 01XX all select the bypass register
when JTAG compliance is enabled. Values 00XX control the
AD6426 I/O as defined in Mode A, and therefore should not
be used in any other mode.
This Information applies to a product under development. Its characteristics and specifications are subject to change without notice. Analog Devices assumes no
obligation regarding future manufacture unless otherwise agreed to in writing. No responsibility is assumed by Analog Devices for its use; nor for any
infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent
rights of Analog Devices.
Revision Preliminary 2.3 (June 9, ´98)
Preliminary Technical Information
T D I
163
Name
JTAGEN
TCK
TMS
TDI
TDO
4
8
162
Figure 10. JTAG Registers
7
Table 20. Test Interface
3
I/O
Instruction Register
O
Boundary Register
6
I
I
I
I
Bypass Register
161
Bist Register
5
Function
JTAG enable (internal pull
down resistor)
JTAG test clock input
JTAG test mode select
JTAG test data input
JTAG test data output
1
4
3
3
2
2
2
1
1
T D O
1
- 27 -
ExTest Instruction
The ExTest instruction is used to force input or output
conditions on the boundary scan cell.
Clamp Instruction
This optional public instruction is similar to the Bypass
instruction, except that once loaded, it will force the values
held in the boundary scan chain onto the corresponding
outputs of the device. This enables all output and bi-
directional pads to be fixed, allowing other parts on the PC-
board to be tested without interference from the AD6426,
while at the same time selecting the Bypass register for the
shortest possible scan path.
All input activity to the AD6426 will be ignored during this
time, since all inputs are driven from the preloaded values in
the boundary scan chain. Typically therefore this instruction
would be preceded by the Sample/Preload instruction. This
instruction is only valid during the normal operation of the
AD6426; i.e. in Mode A.
Sample/Preload Instruction
The Sample/Preload instruction is fully IEEE compliant.
Boundary Register
The boundary cell structure is based on the I/O definition in
Mode A, and hence pins which are outputs only in this mode,
but become inputs in another mode, do not support input scan
cells, and vice versa. Table 22 shows the complete Boundary
register.
Instr.
Register
4 3 2 1
0 0 0 0
0 0 0 1
0 0 1 0
0 0 1 1
0 1 0 0 -
0 1 0 1
0 1 1 0
0 1 1 1
1 0 0 0 -
1 1 1 0
1 1 1 1
Code
ExTest
Clamp
Sample/PreLoad
DoBist
Mode D
Bypass
Bypass
Table 21. JTAG Instructions
Confidential Information
Comments
Public Instruction
Optional Public Instruction
Public Instruction
Private Instruction
Engineering Mode Test
Reserved
Private Instruction
H8 Emulation
Reserved
Public Instruction
Selects Mode A
Public Instruction
Selects Mode A (default)
AD6426

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