QUAD GIGABIT ETHERNET DEVICE
S2204
edge of TCK. All input pins, including clocks, that
have boundary scan are observe only. They can be
sampled in either normal operational or test mode.
All output pins that have boundary scan, are observe
and control. They can be sampled as they are driven
out of the chip in normal operational mode, and they
can be driven out of the chip in test mode using the
Extest instruction. Since JTAG testing operates only
on digital signals there are some pins with analog
signals that JTAG does not cover. The JTAG imple-
mentation has the three required instruction, Bypass,
Extest, and Sample/Preload.
OTHER OPERATING MODES
Operating Frequency Rate
The S2204 is designed to operate at the Gigabit
Ethernet rate of 1.250 GHz.
Loopback Mode
When loopback mode is enabled, the serial data
from the transmitter is provided to the serial input of
the receiver, as shown in Figure 9. This provides the
ability to perform system diagnostics and off-line
testing of the interface to verify the integrity of the
serial channel. Loopback mode is enabled indepen-
dently for each channel using its respective
loopback-enable input, LPEN.
Instruction
Code
BYPASS
EXTEST
SAMPLE/PRELOAD
ID CODE
11
00
01
10
TEST MODES
The RESET pin is used to initialize the Transmit
FIFOs and must be asserted (LOW) prior to entering
the normal operational state (see section Transmit
FIFO Initialization).
JTAG Instruction Description:
The BYPASS register contains a single shift-register
stage and is used to provide a minimum-length serial
path between the TDI and TDO pins of a component
when no test operation of that component is re-
quired. This allows more rapid movement of test
data to and from other components on a board that
are required to perform test operations.
Figure 9. S2204 Diagnostic Loopback Operation
CSU
The EXTEST instruction allows testing of off-chip cir-
cuitry and board level interconnections. Data would
typically be loaded onto the latched parallel outputs
of boundary-scan shift-register stages using the
SAMPLE/PRELOAD instruction prior to selection of
the EXTEST instruction.
CRU
Note: Serial output data remains active during loopback opera-
tion to enable other system tests to be performed.
The SAMPLE/PRELOAD instruction allows a snap-
shot of the normal operation of the component to be
taken and examined. It also allows data values to be
loaded onto the latched parallel outputs of the
boundary-scan shift register prior to selection of the
other boundary-scan test instructions.
JTAG TESTING
The JTAG implementation for the S2204 is compli-
ant with the IEEE1149.1 requirements. JTAG is used
to test the connectivity of the pins on the chip. The
TAP, (Test Access Port), provides access to the test
logic of the chip. When TRST is asserted the TAP is
initialized. TAP is a state machine that is controlled
by TMS. The test instruction and data are loaded
through TDI on the rising edge of TCK. When TMS is
high the test instruction is loaded into the instruction
register. When TMS is low the test data is loaded
into the data register. TDO changes on the falling
The following table provides a list of the pins that are
JTAG tested. Each port has a boundary scan regis-
ter (BSR), unless otherwise noted. The following fea-
tures are described: the JTAG mode of each
register (input, output2, or internal (refers to an inter-
nal package pin)), the direction of the port if it has a
boundary scan register (in or out), and the position
of this register on the scan chain.
11
October 9, 2000 / Revision E
AMCC [ APPLIED MICRO CIRCUITS CORPORATION ]
