VITESSE
SEMICONDUCTOR CORPORATION
Preliminary Datasheet
VSC6424
500 Mb/s Video
Shift Register IC
The Output Phase Shift (OPS) signal gives the capability of selecting which edge of the high speed clock
the DOUT data is synchronized to. When
OPS
is low,
DOUT
comes out on the rising edge of
CLK.
When
OPS
is high,
DOUT
comes out on the falling edge of
CLK.
The high speed output clock (CLKOUT) is not affected by
the state of
OPS.
External Timing
To provide a functional replacement for older designs using the Bt424, formerly manufactured by Brook-
Tree, the VSC6424 provides an external timing mode. This can be accomplished by setting the INT/EXTN pin
low to bypass the internal timing generator. In this case the load and shift timing signals are provided through
the Shift Enable(SEN), Shift Register Load Control(SLDN), and the Latch Load Control(LLDN) pins.
The VSC6424 has two cycles of propagation delay in multiplexer mode where the Bt424 only has one. This
provides the ability to control on which edge of the output clock the output data is clocked on. With the Output
Phase Select (OPS) pin low the output data (DOUT) is synchronous with the positive edge of CLKOUT, where
if OPS is high the output data is synchronous to the negative edge of CLKOUT. See Figure 6 for a timing dia-
gram example with OPS low.
The shift register can also be loaded with serial data while in external timing mode. This is accomplished by
inputting data into the shift register through the Serial Input (SIN) pin. The data is latched on the rising edge of
the CLK while SLDN is high and SEN is low. The data is then shifted to the output pins on each clock cycle
once Shift Enable (SEN) is set high.
I/O Mapping
There are 10 high speed ECL data inputs and 8 high speed ECL data outputs. Some configurations of oper-
ation do not use all these inputs and outputs. The state of the outputs not being used in a given mode is not guar-
anteed. The following two tables, Table 2 and Table 3, show how the high speed bus (DOUT or DIN) maps to
the low speed bus (SB) for a given configuration.
Data is taken and supplied LSB first. The numbers in the table cells refers to the data bit on the low speed
bus (SB<0:39>). They are the inputs in MUX mode and the outputs in DEMUX mode.
Table 2: MUX Mode SB to DOUT Cross Reference
S<2:0>
000
001
010
011
100
101
110
111
Modulus
8 4:1
8 5:1
5 8:1
4 10:1
2 16:1
2 20:1
1 32:1
1 40:1
DOUT7
28-31
35-39
32-39
DOUT6
24-27
30-34
24-31
30-39
16-32
DOUT5
20-23
25-29
DOUT4
16-19
20-24
16-23
20-29
20-39
DOUT3
12-15
14-19
DOUT2
8-11
10-14
8-15
10-19
0-15
DOUT1
4-7
5-9
DOUT0
0-3
0-4
0-7
0-9
0-19
0-31
0-39
G52236-0, Rev 3.0
7/13/99
©
VITESSE
SEMICONDUCTOR CORPORATION
741 Calle Plano, Camarillo, CA 93012 • 805/388-3700 • FAX: 805/987-5896
Page 3
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