
PEB 3445 E
Interface Description
Data Sheet
71
2001-06-29
contains a total of n = 484 scan cells. The desired test mode is selected by serially
loading a 4-bit instruction code into the instruction register via TDI (LSB first).
EXTEST
is used to examine the interconnection of the devices on the board. In this test
mode at first all input pins capture the current level on the corresponding external
interconnection line, whereas all output pins are held at constant values (‘0’ or ‘1’). Then
the contents of the boundary scan is shifted to TDO. At the same time the next scan
vector is loaded from TDI. Subsequently all output pins are updated according to the new
boundary scan contents and all input pins again capture the current external level
afterwards, and so on.
INTEST
supports internal testing of the chip, i. e. the output pins capture the current level
on the corresponding internal line whereas all input pins are held on constant values (‘0’
or ‘1’). The resulting boundary scan vector is shifted to TDO. The next test vector is
serially loaded via TDI. Then all input pins are updated for the following test cycle.
SAMPLE/PRELOAD
is a test mode which provides a snapshot of pin levels during
normal operation.
IDCODE
: A 32-bit identification register is serially read out via TDO. It contains the
version number (4 bits), the device code (16 bits) and the manufacturer code (11 bits).
The LSB is fixed to ‘1’.
The ID code field is set to
Version
: 1
H
Part Number
: 0078
H
Manufacturer
: 083
H
(including LSB, which is fixed to ’1’)
Note: Since in test logic reset state the code ‘0011’ is automatically loaded into the
instruction register, the ID code can easily be read out in shift DR state.
BYPASS
: A bit entering TDI is shifted to TDO after one TCK clock cycle.
CLAMP
allows the state of signals driven from component pins to be determined from
the boundary-scan register while the bypass register is selected as the serial path
between TDI and TDO. Signals driven from the TE3-MUX will not change while the
CLAMP instruction is selected.
HIGHZ
places all of the system outputs in an inactive drive state.