
6
QUAD SERIAL BACKPLANE DEVICE
S2064
October 13, 2000 / Revision G
Table 1. Input Modes
K
C
O
L
N
A
H
C
E
D
O
M
T
n
o
r
e
p
O
0
0
r
d
e
s
)
u
w
K
k
L
C
F
s
d
E
R
.
e
b
E
D
r
O
M
v
c
K
L
e
o
C
F
N
(
E
R
L
.
n
A
n
M
a
R
h
c
O
N
l
e
0
1
k
c
)
w
o
e
k
o
s
d
d
e
s
u
e
b
x
K
r
L
C
v
c
T
.
E
e
o
D
N
O
M
(
O
K
L
C
F
T
L
l
A
M
o
R
O
a
d
N
1
0
.
E
.
D
O
O
F
I
M
F
K
L
l
C
F
E
o
)
R
.
E
d
v
a
D
k
O
c
w
e
M
K
C
o
s
d
O
d
L
e
s
e
b
L
u
E
K
r
N
L
N
C
v
c
A
F
H
E
e
C
R
R
(
a
o
k
1
1
.
E
.
D
O
O
F
I
M
F
A
K
l
o
L
t
C
T
n
a
)
.
E
a
D
d
v
a
O
k
w
M
c
e
k
K
o
s
d
C
o
O
t
L
d
L
s
b
E
u
N
A
r
N
K
v
c
A
L
H
C
e
R
C
T
(
t
e
e
1. Note that internal synchronization of FIFOs is performed upon de-assertion of
RESET.
TRANSMITTER DESCRIPTION
The transmitter section of the S2064 contains a
single PLL which is used to generate the serial rate
transmit clock for all transmitters. Four channels are
provided with a variety of options regarding input
clocking and loopback. The transmitters can operate
in the range of 0.77 GHz to 1.3 GHz, 10 or 20 times
the reference clock frequency.
Data Input
The S2064 has been designed to simplify the paral-
lel interface data transfer and provides the utmost in
flexibility regarding clocking of parallel data. Prior, or
less sophisticated, implementations of this function
have either forced the user to synchronize transmit
data to the reference clock or to provide the output
clock as a reference to the PLL, resulting in in-
creased jitter at the serial interface. The S2064 in-
corporates a unique FIFO structure on both the
parallel inputs and the parallel outputs which en-
ables the user to provide a “clean” reference source
for the PLL and to accept a separate external clock
which is used exclusively to reliably clock data into
the device.
Data is input to each channel of the S2064 nominally
as a 10 bit wide word. This consists of eight data bits
of user data, KGEN, and SOF. An input FIFO and a
clock input, TCLKx, are provided for each channel of
the S2064. The device can operate in two different
modes. In CHANNEL LOCK mode all four bytes of
input data are clocked into their respective FIFOs
using a common clock. The S2064 can be config-
ured to use either the TCLKA (TCLK MODE) input or
the REFCLK input (REFCLK MODE). In NORMAL
mode, each byte of data is clocked into its FIFO with
the TCLKx provided with each byte. Table 1 provides
a summary of the input modes for the S2064.
Operation in the TCLK MODE makes it easier for
users to meet the relatively narrow setup and hold
time window required by the parallel 10-bit interface.
The TCLK signal is used to clock the data into an
internal holding register and the S2064 synchronizes
its internal data flow to insure stable operation. How-
ever, regardless of the clock mode, REFCLK is al-
ways the VCO reference clock. This facilitates the
provision of a clean reference clock resulting in mini-
mum jitter on the serial output. The TCLK must be
frequency locked to REFCLK, but may have an arbi-
trary but fixed phase relationship. Adjustment of in-
ternal timing of the S2064 is performed during reset.
Once synchronized, the S2064 can tolerate up to
±
3ns of phase drift between TCLK and REFCLK.
Figure 6 demonstrates the flexibility afforded by the
S2064. A low jitter reference is qovided directly to
the S2064 at either 1/10 or 1/20 the serial data rate.
This insures minimum jitter in the synthesized clock
used for serial data transmission. A system clock
output at the parallel word rate, TCLKO, is derived
from the PLL and provided to the upstream circuit as
a system clock. The frequency of this output is con-
stant at the parallel word rate, 1/10 the serial data
rate, regardless of whether the reference is provided
at 1/10 or 1/20 the serial data rate. This clock can be
buffered as required without concern about added
delay. There is no phase requirement between
TCLKO and TCLKx, which is provided back to the
S2064, other than that they remain within
±
3ns of
the phase relationship established at reset.