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Test Signals - Motorola MC68838 User Manual

Media access controller
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Address Match ( MATCH )
This TTL-level input indicates to the MAC whether the start of frame information
presented to the CAM matches an individual or multicast group address stored in the
CAM or whether the bridge routing logic wants to accept the frame based on its
algorithm. MATCH is asserted (low) upon a match. The MAC ignores this signal when
receiving frames with 16-bit addresses.
This signal need only be valid for one BYTCLK cycle. When this signal is asserted (low),
the received frame matches the station's receive criteria, and the MAC takes SA or DA
actions per Table 9-1.


The test interface is a BYTCLK-synchronous interface used to support boundary scan
testing and segmented counting of all internal MAC counters.
MAC Test Mode Controls (MTEST1–MTEST0)
These TTL-level input lines determine the operating mode of the chip's diagnostics.
BIST is designed to work at full speed with BYTCLK at 12.5 MHz; therefore, these
signals must be synchronous with BYTCLK.
00 = Normal operating mode.
01 = COUNTER_TEST mode. All chip counters are incremented in groups of four
10 = BOUNDARY_SCAN mode. All I/O registers act as shift registers so that
boundary scan diagnostics may be performed using the MSCANI and MSCANO
11 = Reserved for future use. The MAC will currently treat this as normal operating
Serial Scan In (MSCANI)
This TTL-level input signal is used to shift a particular bit pattern into the boundary scan
latches. High represents a one; low represents a zero. This signal must be synchronous
with BYTCLK and is only active when MTESTx indicates BOUNDARY_SCAN mode
(i.e., MTESTx = 10).
Serial Scan Out (MSCANO)
This CM0S-level output signal is used to scan out data contained in the boundary scan
latches. Its value is synchronous with BYTCLK, and it is only valid when MTESTx
indicates BOUNDARY_SCAN mode (i.e., MTESTx = 10); otherwise, the output is
Parametric Test Out (MPTSTO)
This output signal, which is driven by a NAND tree of all inputs, allows for DC
parametric testing and AC process performance verification. This signal is not intended
for use by the user and should not be connected.
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