6-4
MC92603 Quad Gigabit Ethernet Transceiver Reference Manual
MOTOROLA
System Accessible Test Modes
6.2
System Accessible Test Modes
System accessible test modes are selected through the TST_0, TST_1, and XCVR_A_LBE
signals. Table 6-4 shows test mode state selection.
6.2.1
Loopback System Test
Each channel of MC92603 may be individually configured for digital loopback, where the
transmitted data is looped back to its receiver independent of the receiver’s link inputs. This
is enabled by asserting XCVR_x_LBE (where ‘x’ is channel A through D) high. The code
groups transmitted are controlled by the normal transmitter controls. If the transceiver is
working properly, the data/control code groups transmitted are received internally by the
receiver. This allows system logic to use various data sequences to test the operation of the
transceiver.
The loopback signals are electrically isolated from the XLINK_x_P and XLINK_x_N
output signals. Therefore, if the outputs are externally shorted, or otherwise restricted, the
loopback signals still function normally. When in loopback mode, the XLINK_x_P and
XLINK_x_N output signals will continue to operate normally.
The receiver’s link input signals, RLINK_x_P and RLINK_x_N, are electrically isolated
during loopback mode, such that their state does not affect the loopback path.
LBOE controls the state of the XLINK_x_P/XLINK_x_N output signals during loopback
testing. If LBOE is low, XLINK_x_P/XLINK_x_N are held to low and high, respectively.
If LBOE is high, data is present on XLINK_x_P/XLINK_x_N.
Table 6-4. Test Mode State Selection
TST_1
TST_0
XCVR_A_LBE
Description
Low
Low
Low
Normal operation. No test mode enabled.
Low
Low
High
1
1
If TST_1 and TST_0 are both low, each channel is controlled by its own LBE (channel A = XCVR_A_LBE,
channel B = XCVR_B_LBE, etc.). If either TST_1 or TST_0 is high, then XCVR_A_LBE is used to select
BIST test modes for all channels, and XCVR_B_LBE, XCVR_C_LBE, and XCVR_D_LBE are ignored.
Internal loopback system test mode
Low
High
Low
System BIST sequence—external loopback—no idles inserted
Low
High
High
System BIST sequence—external loopback—with idles inserted
High
Low
Low
System BIST sequence—internal loopback—with idles inserted
High
Low
High
Reserved
High
High
Low
Reserved
High
High
High
Reserved
Summary of Contents for MC92603
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