User Manual
BCM1250/BCM1125/BCM1125H
10/21/02
B r o a d c o m C o r p o r a t i o n
Document
1250_1125-UM100CB-R
Section 15: JTAG and Debug Page
433
To use the boundary scan and EXTEST to test board connectivity the following steps should be performed:
1
The TAP controllers of both parts under test are set to the EXTEST instruction.
2
The desired pattern on the output pins is shifted into the BSR shadow register.
3
The Update-DR state is traversed.
4
The Capture-DR state of the target part is traversed.
5
The contents of the shadow register in the target part is scanned out and then compared to expected results.
To use boundary scan and INTEST to run test vectors against the part the following steps should be performed:
1
The instruction register for the part is set to the INTEST instruction.
2
The desired test pattern is scanned into the shadow register.
3
The Update-DR state is traversed.
4
The Capture-DR state is traversed.
5
The results from the vector are scanned out from the shadow register. At the same time the next test pattern
can be scanned in.
The differential signals on the HyperTransport interface are scanned a little differently. All of these are
unidirectional, but the signals are also differential and double data rate. The data rate is doubled and the
differential is formed in the output pads, the differential is received and the data rate halved in the input pads.
shows the output cell. In normal operation two bits of data are presented, one for transmission when
the clock is high the other when the clock is low. The inverted version of these bits drives the negative output
of the differential pair. The scan function uses two BC_1 cells, one drives each of the pins, but rather than the
pin data they monitor the single data rate version of the data. Thus when performing EXTEST the two pins are
separate (although they should be driven as inverses to guarantee correct reception), but when scanning out
vectors the data for both edges of the clock can be captured.
Figure 86: JTAG HyperTransport Output Boundary Scan Block
TDI
Out_clk_h
ldt_tx_clk
Mode
tx_p
update_dr
clock_dr
tx_n
shift_dr
TDO
Out_clk_l
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