DS90CP04_07 Datasheet, PDF (12/18 Pages) National Semiconductor (TI) – 1.5 Gbps 4x4 LVDS Crosspoint Switch

FIGURE 10. Configuration and Output Enable/Disable Timing
20028720
Functional Descriptions
PROGRAMMING WITH THE SERIAL INTERFACE
The configuration of the internal multiplexer is programmed
through a simple serial interface consisting of serial clock
SCLK and serial input data line SI. The serial interface is de-
signed for easy expansion to larger switch array. A replicated
output serial interface (RSCLK, RSO) is provided for propa-
gating the control data to the downstream device in the row
of an array of DS90CP04 devices in a matrix. A similar repli-
cated serial interface (CSCLK, CSO) is provided for propa-
gating the control data to the downstream devices in the first
column of the device matrix. Through this scheme, user can
program all the devices in the matrix through one serial control
bus (SCLK and SI) with the use of the feed-through replicated
control bus at RSCLK and RSO, CSCLK and CSO.
To program the configuration of the switch, a 30-bit control
word is sent to the device. The first 6 bits shift the start frame
into SI. The only two valid start frames are 1F'h for a config-
uration load and 1E'h for a configuration read. The start frame
is followed by the row and column addresses of the device to
be accessed, as well as the switch configuration of the four
channels of the device. Table 1 and Table 2 are the bit defi-
nitions of the control word. D29 is the first bit that shifts into
SI.
TABLE 1. 30-Bit Control Word
Bit
D29–D24
D23–D18
D17–D12
D11–D9
D8–D6
D5–D3
D2–D0
Bit Length
Descriptions
6
The start frame for control word synchronization (01 1111'b = LOAD).
6
Specify the row address of the device to be access. The serial interface can access up to 64 devices in
the row.
6
Specify the column address of the device to be access. The serial interface can access up to 64 devices
in the column.
3
Specify the switch configuration for Output 1. See Table 2.
3
Specify the switch configuration for Output 2. See Table 2.
3
Specify the switch configuration for Output 3. See Table 2.
3
Specify the switch configuration for Output 4. See Table 2.
TABLE 2. Switch Configuration Data
MSB
LSB OUT1± Connects to
OUT2± Connects to
OUT3± Connects to
OUT4± Connects to
0
0
0 Output 1 Tri-Stated
Output 2 Tri-Stated
Output 3 Tri-Stated
Output 4 Tri-Stated
0
0
1 IN1±
IN1±
IN1±
IN1±
0
1
0 IN2±
IN2±
IN2±
IN2±
0
1
1 IN3±
IN3±
IN3±
IN3±
1
0
0 IN4±
IN4±
IN4±
IN4±
www.national.com
12