Philips PTN3501 Quasi-bidirectional I/Os (see Figure 13)

Philips Semiconductors Product specification

PTN3501Maintenance and control device

2001 Jan 17 7

Quasi-bidirectional I/Os (see Figure 13)

A quasi-bidirectional I/O can be used as an input or output without the use of a control signal for data direction. At power-on the I/Os are HIGH.

In this mode, only a current source to VDD is active. An additional strong pull-up to VDD allows fast rising edges into heavily loaded outputs.

These devices turn on when an output is written HIGH, and are switched off by the negative edge of SCL. The I/Os should be HIGH before

being used as inputs.

S 0 A2 A1 A0 0 A A ASDA

SCL 12345678

SW00789

ACKNOWLEDGE

FROM SLAVE

R/WSTART CONDITION ACKNOWLEDGE

FROM SLAVE

SLAVE ADDRESS (PTN3501) DATA TO PORT DATA TO PORT

OUTPUT

VOLTAGE

PULL-UP

OUTPUT

CURRENT IOHt IOH

A5A4A3

Figure 13. Transient pull-up current IOHt while P3 changes from LOW-to-HIGH and back to LOW

SYMBOL PARAMETER MIN TYP MAX UNIT

tpv Output data valid; CL ≤ 100 pF – – 4 µs

tps Input data setup time; CL ≤ 100 pF 0 – – µs

tph Input data hold time; CL ≤ 100 pF 4 – – µs

tiv Interrupt input data valid time;

CL ≤ 100 pF – – 4 µs

tir Interrupt reset time; CL ≤ 100 pF – – 4 µs