ds4550et-r Maxim Integrated Products, Inc., ds4550et-r Datasheet - Page 11

• Manufacturer Part Number: ds4550et-r
• Description: Ds4550 I?c And Jtag Nonvolatile 9-bit I/o Expander Plus Memory
• Manufacturer: Maxim Integrated Products, Inc.

Update-DR. A falling edge on TCK while in the
Update-DR state latches the data from the shift regis-
ter path of the test data registers into a set of output
latches. This prevents changes at the parallel output
because of changes in the shift register. On the rising
edge of TCK, the controller goes to the Run-Test/Idle
state if TMS is LOW or it goes to the Select-DR-Scan
state if TMS is HIGH.
Select-IR-Scan. All test data registers retain their previ-
ous state. The Instruction Register remains unchanged
during this state. With TMS LOW, a rising edge on TCK
moves the controller into the Capture-IR state. TMS
HIGH during a rising edge on TCK puts the controller
back into the Test-Logic-Reset state.
Capture-IR. The Capture-IR state is used to load the
shift register in the Instruction Register with a fixed
value. This value is loaded on the rising edge of TCK. If
TMS is HIGH on the rising edge of TCK, the controller
enters the Exit1-IR state. If TMS is LOW on the rising
edge of TCK, the controller enters the Shift-IR state.
Shift-IR. In this state, the shift register in the Instruction
register is connected between TDI and TDO and shifts
data one stage for every rising edge of TCK toward the
TDO serial output while TMS is LOW. The parallel out-
puts of the Instruction Register as well as all test data
registers remain at their previous states. A rising edge
on TCK with TMS HIGH moves the controller to the
Exit1-IR state. A rising edge on TCK with TMS LOW
keeps the controller in the Shift-IR state while moving
data one stage through the Instruction Shift Register.
Exit1-IR. A rising edge on TCK with TMS LOW puts
the controller in the Pause-IR state. If TMS is HIGH on
the rising edge of TCK, the controller enters the
Update-IR state.
Pause-IR. Shifting of the Instruction shift register is halt-
ed temporarily. With TMS HIGH, a rising edge on TCK
puts the controller in the Exit2-IR state. The controller
remains in the Pause-IR state if TMS is LOW during a
rising edge on TCK.
Exit2-IR. A rising edge on TCK with TMS HIGH puts the
controller in the Update-IR state. The controller loops
back to Shift-IR if TMS is LOW during a rising edge of
TCK in this state.
Update-IR. The instruction code that has been shifted
into the Instruction shift register is latched to the paral-
lel outputs of the Instruction Register on the falling
edge of TCK as the controller enters this state. Once
latched, this instruction becomes the current instruc-
tion. A rising edge on TCK with TMS LOW puts the con-
troller in the Run-Test/Idle state. With TMS HIGH, the
controller enters the Select-DR-Scan state.
I
2
C and JTAG Nonvolatile 9-Bit I/O
____________________________________________________________________
Expander Plus Memory
The Instruction Register contains a shift register as well
as a latched parallel output and is 4 bits in length. When
the TAP controller enters the Shift-IR state, the Instruction
shift register is connected between TDI and TDO. While
in the Shift-IR state, a rising edge on TCK with TMS LOW
shifts the data one stage toward the serial output at TDO.
A rising edge on TCK in the Exit1-IR state or the Exit2-IR
state with TMS HIGH moves the controller to the Update-
IR state. The falling edge of that same TCK latches the
data in the Instruction shift register to the Instruction
Register parallel output. Instructions supported by the
DS4550 and its respective operational binary codes are
shown in
SAMPLE/PRELOAD. This is a mandatory instruction
for the IEEE 1149.1 specification that supports two
functions. The digital I/Os of the device can be sam-
pled at the Boundary Scan test data register without
interfering with the normal operation of the device by
using the Capture-DR state. SAMPLE/PRELOAD also
allows the device to shift data into the Boundary Scan
test data register through TDI using the Shift-DR state.
BYPASS. When the BYPASS instruction is latched into
the Instruction register, TDI connects to TDO through
the 1-bit Bypass test data register. This allows data to
pass from TDI to TDO without affecting the device’s
normal operation.
EXTEST. This instruction allows testing of all intercon-
nections to the device. When the EXTEST instruction is
latched in the Instruction register, the following actions
occur. Once enabled through the Update-IR state, the
parallel outputs of all digital output pins are driven. The
Boundary Scan test data register is connected between
TDI and TDO. The Capture-DR samples all digital
inputs into the Boundary Scan test data register.
Table
SAMPLE/PRELOAD
BYPASS
EXTEST
CLAMP
HIGHZ
IDCODE
ADDRESS
READ
WRITE
INSTRUCTION
2. Instruction Codes
Table
2 below.
Boundary Scan
Bypass
Boundary Scan
Bypass
Bypass
Identification
Memory Address
Memory Read
Memory Write
SELECTED
REGISTER
Instruction Register
INSTRUCTION
CODE
0010
1111
0000
0011
0100
0001
1001
1010
1011
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