MOTOROLA
Chapter 2. Transmitter
2-7
Backplane Application Modes (COMPAT = Low)
The 8B/10B code set includes 12 special control codes. Special control codes may be
transmitted by setting the XMIT_x_K high as indicated in Table 2-3. There are only 12
valid control code groups; if the data input is other than the 12 defined values, then an
illegal 10-bit code group will be generated and transmitted. Invalid combinations of
XMIT_x_K and XMIT_x_7–XMIT_x_0 will generate invalid 10-bit code groups.
If XMIT_x_ERR is high then the 8B/10B encoder is forced to produce an invalid 10-bit
code.
When using the device in a system where word alignment is required, it may be desirable
to generate disparity-style word synchronization events. Also, it may be necessary to
generate a disparity-style synchronization event for compatibility with legacy transceivers.
A disparity-style word synchronization event is generated by setting the transmit data
inputs to a 0xAD and asserting XMIT_x_K high for the appropriate transmitter(s). The
transmitter generates 1 of 2 unique 16-code group IDLE (K28.5) sequences depending on
the current running disparity:
I+, I+, I–, I–, I+, I–, I+, I–, I+, I–, I+, I–, I+, I–, I+, I–
or
I–, I–, I+, I+, I–, I+, I–, I+, I–, I+, I–, I+, I–, I+, I–, I+
where I+ stands for K28.5 of positive disparity, and I– stands for K28.5 of negative
disparity.
The transmitter inputs, XMIT_x_7–XMIT_x_0, XMIT_x_K, XMIT_x_ERR, and
XMIT_x_ENABLE are ignored for the next 15 byte-times while this 16-code group
sequence is transmitted.
Transmitting uncoded data in backplane applications with the reduced interface mode is
shown in Table 2-4. The transmitter functional operation is the same as discussed above,
except the data is entered on both edges of the transmitter input clock, XMIT_x_CLK.
The 8 bits of uncoded data are entered with the least significant nibble on the rising clock
and the most significant nibble on the falling clock edge.
NOTE
When operating with the reduced data interface the MC92603
input pins, XMIT_x_7–XMIT_x_4, are unused and should be
terminated low.
Table 2-4. Transmitter Inputs for Reduced Uncoded Data—Backplane Mode
Data on Rising Edge of XMIT_x_CLK
Data on Falling Edge of XMIT_x_CLK
MC92603 Signal Name
XMIT_x_ENABLE
XMIT_x_ENABLE (XOR) XMIT_x_ERR
XMIT_x_ENABLE
XMIT_x_K
Unused
XMIT_x_K
Data bits 3–0
Data bits 7–4
XMIT_x_3/XMIT_x_0
Содержание MC92603
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