10

4421B–ASSP–10/05

TSSIO16E

4.5

State on power on and safety mode

This table indicates the state of ports A and B and the INT pin on power on and changeover to

the safety mode. In power on mode the command register is initialized to 0.

• selection of RDX0 acces in automatic mode,

• line diagnosis activated,

• access free peripheral.

4.5.1

Condition for enter in safety mode (see Figure )

4.5.2

Condition for exit from safety mode

Writing of port A is a way of exiting from the safety mode. Pin INT returns to 0.

Example: Case of a LCD display with a TSSIO16E shared simul-

taneously by car radio and vehicle computer. In this case, the car

radio (B7 = 1) inhibits access to the display line until the full mes-

sage is displayed.

This access control strategy is only meaningful if the computer

(car radio or on-board computer) wants access to the peripheral

(display) and reads the control register to ensure that the periph-

eral is available. Writing to the port is never inhibited.

car radio

VAN lines

VAN lines

vehicle computer

LCD display with TSSIO16E

power-on

safety mode

Port A

high Z

high Z

Port B

high Z

unchanged

INT pin

0

1

• After reset:

in the absence of writing or reading in the circuit for a SLTO

• During operation:

in the presence of coherent frames but the absence of reading or writing in the circuit for a LTO