
2004 Jul 22
81
Philips Semiconductors
Product specication
Multistandard video decoder with adaptive
comb lter and component video input
SAA7118
10 BOUNDARY SCAN TEST
The SAA7118 has built-in logic and 5 dedicated pins to
support boundary scan testing which allows board testing
without special hardware (nails). The SAA7118 follows the
“IEEE Std. 1149.1 - Standard Test Access Port and
Boundary-Scan Architecture” set by the Joint Test Action
Group (JTAG) chaired by Philips.
The 5 special pins are Test Mode Select (TMS), Test
Clock (TCK), Test Reset (TRST), Test Data Input (TDI)
and Test Data Output (TDO).
The Boundary Scan Test (BST) functions BYPASS,
EXTEST, INTEST, SAMPLE, CLAMP and IDCODE are all
supported; see Table
35. Details about the JTAG
BST-TEST can be found in specification “IEEE Std.
1149.1”. A file containing the detailed Boundary Scan
Description Language (BSDL) description of the SAA7118
is available on request.
Table 35 BST instructions supported by the SAA7118
INSTRUCTION
DESCRIPTION
BYPASS
This mandatory instruction provides a minimum length serial path (1 bit) between TDI and TDO
when no test operation of the component is required.
EXTEST
This mandatory instruction allows testing of off-chip circuitry and board level interconnections.
SAMPLE
This mandatory instruction can be used to take a sample of the inputs during normal operation of the
component. It can also be used to preload data values into the latched outputs of the boundary scan
register.
CLAMP
This optional instruction is useful for testing when not all ICs have BST. This instruction addresses
the bypass register while the boundary scan register is in external test mode.
IDCODE
This optional instruction will provide information on the components manufacturer, part number and
version number.
INTEST
This optional instruction allows testing of the internal logic (no customer support available).
USER1
This private instruction allows testing by the manufacturer (no customer support available).
10.1
Initialization of boundary scan circuit
The Test Access Port (TAP) controller of an IC should be
in the reset state (TEST_LOGIC_RESET) when the IC is
in functional mode. This reset state also forces the
instruction register into a functional instruction such as
IDCODE or BYPASS.
To solve the power-up reset, the standard specifies that
the TAP controller will be forced asynchronously to the
TEST_LOGIC_RESET state by setting the TRST pin
LOW.
10.2
Device identication codes
A device identification register is specified in “IEEE Std.
1149.1b-1994”. It is a 32-bit register which contains fields
for the specification of the IC manufacturer, the IC part
number and the IC version number. Its biggest advantage
is the possibility to check for the correct ICs mounted after
production and determination of the version number of ICs
during field service.
When the IDCODE instruction is loaded into the BST
instruction register, the identification register will be
connected between pins TDI and TDO of the IC. The
identification register will load a component specific code
during the CAPTURE_DATA_REGISTER state of the TAP
controller and this code can subsequently be shifted out.
At board level this code can be used to verify component
manufacturer, type and version number. The device
identification register contains 32 bits, numbered 31 to 0,
where bit D31 is the most significant bit (nearest to TDI)
and bit D0 is the least significant bit (nearest to TDO);