Aeroflex Circuit Technology

SCDCT2500 REV A 6/12/98 Plainview NY (516) 694-6700

3

I/O FUNCTION LISTING

NAME

I/O

DESCRIPTION

SO/SI

I

Source / Sink Mode Select

Determines the overall Functioning Mode of the Device.

"1"= Source emulation. This mode enables the chip to send control frames, single

command and data words and burst data. It is able to receive control frames.

"0" = Sink emulation. In this mode, the chip can only send control frames. It can

receive control frames, command words, single data words and burst data.

DO-D31

I/O

Parallel Bi-directional Data Bus (Internal Pullups)

Source Mode: Input to 32 bit transmit data latch

Sink Mode: Tri-state output from 32 bit received data latch

D/E

I

Type D / Type E Control Frame Length Select (Internal Pulldown)

"1" = Three bit control frames are transmitted and the received control frame is

checked for a proper three bit length.

"0" = Four bit control frames are transmitted and the received control frame is checked

for a proper four bit length.

PAREN

I

Parity Enable (Internal Pullup)

"1" = Parity bit is generated in Source mode and checked for in Sink mode.

"0" = No parity is generated or checked for.

POE

I

Parity Odd or Even Select (Internal Pullup)

"1" = Odd parity

"0" = Even parity

CLK

I

System Clock

20 megahertz with 50% duty cycle

BURST

I

Burst Mode Select

"1" = Data transmission and Reception can be done in Burst mode

"0" = Normal operation

Source Mode: Data words loaded during the transmission of another will be

concatenated to the transmission without addition of SYNC or WI bits. The first word

will have a SYNC bit of "1" and and a WI bit, which must be set to "0". The Burst line

must remain stable for the entire duration of the loading and transmission of the data.

Sink Mode: During a Burst data reception, after the SYNC and WI bits, data words are

picked off at bit count multiples of 32, or 33 with parity enabled, and loaded into the

output latch. The transmission is considered ended when a gap is detected. The line

must be stable during the entire reception.

STR1 and

STR2

I

Strobe One Bar and Strobe Two Bar

Control Strobes for Reading and Writing the Parallel I/O data Latches

Source Mode: STR1 loads data present on DO-D15 into the lower 16 bit input latch

and STR2 loads data on D16-D31 into the upper 16 bit input latch. Upon completion of

STR2, a sequence is initiated to load the entire 32 bits into a shift register and start a

transmission. The lower 16 bits must be loaded prior to or during the load of the upper

16 bits. For a 32 bit load, STR1 and STR2 can be tied together.

Sink Mode: STR1 enables the lower 16 bits of a received word to be output on

D0-D15. STR2 enables the upper 16 bits of a received word to be output on D16-D31.

The entire 32 bits of data must be read before another data reception or it will be

overwritten. If this occurs, the overflow flag, OVRFLOW, will go high. The data is

considered completely read upon the completion of STR2.

CMDIN

O

Command In

Third bit of the Received Control Frame. Valid during RCVCNTRL.

DTAIN

O

Data In

Second bit of the Received Control Frame. Valid during RCVCNTRL.