VITESSE

SEMICONDUCTOR CORPORATION

Data Sheet

VSC880

High Performance 16x16

Serial Crosspoint Switch

Page 10

G52191-0, Rev 4.2

01/05/01

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FI[15:0]Force IDLE register, bit 0 is channel 0 etc

RESY[15:0]Resynch register, bit 0 is channel 0 etc

OE[15:0]Output enable register, bit 0 is channel 0 etc

LPBK[15:0]Facility loopback register, bit 0 is channel 0 etc

1.5 Parallel CPU Interface

There is a parallel 8 bit CPU interface on the VSC880 that can be used to read and write the status and control

registers described above. This is an asynchronous interface that was design to operate with many common micro

controllers that are available. The functional timing diagrams for a write and a read are shown in the following

figures. Timing information can be found in the AC Characteristics section of this data sheet.

Figure 2: CPU Interface Functional Write Cycle Timing

Figure 3: CPU Interface Functional Read Cycle Timing

1.6 Parallel Configuration Interface

In addition to reading and writing the switch configuration using the CPU interface as described above, the entire

switch matrix can be reprogrammed in 4 word clocks by setting the CEN signal LOW. If CEN is set LOW, the

parallel interface DATA[15:0] contains a 16 bit switch configuration input port, the inputs FI[3:0] load the FI bits and

the WEN signal becomes a programming signal as shown in the figure below. It takes 4 word clocks to load all 64 bits

of switch configuration data and 16 FI bits into holding registers. All data transfer timing is relative to REFCLK.

After data has been loaded, and if CCLK is HIGH, all 80 bits of data are strobed into the switch matrix and FI control

logic. Otherwise, the configuration information is stored in holding registers until the next CCLK pulse strobes it in.

Since the CCLK signal is delayed internally in the switch, it can be asserted as early as the WEN signal pulse to

strobe in the configuration information.

ADDR

CWEN

CDATA

CSEL

Valid Data

Valid Address

ADDR

CWEN

CDATA

CSEL

Valid Data

Valid Address

Hi-Z