
DS3171/DS3172/DS3173/DS3174
214
CLAMP.
All digital output pins output data from the boundary scan parallel output while connecting the bypass
register between JTDI and JTDO. The outputs do not change during the CLAMP instruction. If the previous
instruction was not EXTEST, the outputs will be driven according to the values in the boundary scan register at the
positive edge of JTCLK in the Update-IR state. The typical use of this instruction is in a system that has the JTAG
scan chain of multiple chips connected in series, and all of the chips have their outputs initialized using the
EXTEST mode. Then some of the chips are left initialized using the CLAMP mode and others have their IO
controlled using the EXTEST mode. This reduces the size of the scan chain during the partial testing of the system.
13.4 JTAG ID Codes
Table 13-2. JTAG ID Codes
DEVICE
REVISION
ID[31:28]
DEVICE CODE
ID[27:12]
MANUFACTURER’S CODE
ID[11:1]
REQUIRED
ID[0]
DS3171 Consult
factory
0000000001000100
00010100001 1
DS3172 Consult
factory
0000000001000101
00010100001 1
DS3173 Consult
factory
0000000001000110
00010100001 1
DS3174 Consult
factory
0000000001000111
00010100001 1
13.5 JTAG Functional Timing
This functional timing for the JTAG circuits shows:
•
The JTAG controller starting from reset state
•
Shifting out the first 4 LSB bits of the IDCODE
•
Shifting in the BYPASS instruction (111) while shifting out the mandatory X01 pattern
•
Shifting the TDI pin to the TDO pin through the bypass shift register
•
An asynchronous reset occurs while shifting
Figure 13-3. JTAG Functional Timing
JTCLK
JTRST
JTMS
JTDI
JTDO
(STATE)
Reset
X
Run Test
Idle
Select DR
Scan
Capture
DR
Shift
DR
Exit1
DR
Update
DR
Select DR
Scan
Select IR
Scan
Capture
IR
Shift IR
Exit1
IR
Update
IR
Select DR
Scan
Capture
DR
Shift
DR
Test
Logic Idle
(INST)
IDCODE
BYPASS
IDCODE
X
X
X
X
X
Output
Pin
Output pin level change if in "EXTEST" instruction mode
13.6 IO Pins
All input, output, and inout pins are inout pins in JTAG mode.