AS2702 – AS-Interface Slave IC

Revision 1.3, 21-Aug-08

Page 6 of 13

Data Port Pins D3, …, D0 and Data Strobe Pin DSTBn

Basically data port D3, …, D0 is designed for bidirectional data transfer out of and into the slave device. Each data port pin is

equipped with both a low-side open-drain output stage as well as an input stage to this purpose.

Depending on the so-called IO-configuration code, written and stored in the slave device, each data port pin is individually set to

behave as

•

output, or

•

output/input, or

•

input.

The timing of the data transfer is presented in Figure 3.

Strobe signal DSTBn flags and governs the data transfer as follows:

a)

data port pin is set ‘output’:

output data become valid upon the HL-edge of the strobe and will remain so until the next HL-edge, hence during the entire

strobe cycle;

b)

data port pin is set ‘output/input’:

output data become valid upon the HL-edge of the strobe and will remain so until it’s LH-edge; input data to be valid within a

specific time window relative to the HL-edge, after completion of the strobe’s L-phase;

c)

data port pin is set ‘input’:

input data to be valid within a specific time window relative to the HL-edge of the strobe, after completion of the strobe’s

L-phase.

If necessary, output data as per a) and b) can be easily latched with the LH-edge of strobe DSTBn as they will remain valid for

about 0.4µs beyond as a minimum.

Care must be taken however, that signal delay added by external circuitry is lower for the strobe than for the data.

Data in

Data out

Data in

Data out

t

STB

t

t

t

DSTBn

t

INPmin

t

INPmax

Dx

Dx

DSTBn

Figure 3

Timing of data transfer at data port D3, …, D0 relative to strobe DSTBn

The following table specifies the timing parameters relating to Figure 3:

Symbol

Parameter

Min

Max

Unit

Note

tSTB

Delay DSTBn HL-edge to Dx output data valid

1.5

µs

tDSTBn

DSTBn strobe width

6

6.8

µs

1

tOUTOFF

Delay DSTBn LH-edge to Dx output off

0.2

1

µs

2

tINP

Input data valid time window

10.5

12.5

µs

3