AT89C5132-ROTIL datasheet(135/181 Pages) ATMEL

135 / 181 page

135

4173D–USB–02/06

AT89C5132

If the SSAA bit is reset during a transfer, the controller will transmit the last Byte of the transfer

and enter state C0h or C8h. The controller is switched to the not addressed slave mode and will

ignore the master receiver if it continues the transfer. Thus the master receiver receives all 1’s

as serial data. While SSAA is reset, the controller does not respond to its own slave address.

However, the TWI bus is still monitored and address recognition may be resumed at any time by

setting SSAA. This means that the SSAA bit may be used to temporarily isolate the controller

from the TWI bus.

20.1.6

Miscellaneous States

There are 2 SSSTA codes that do not correspond to a defined TWI hardware state (see

Table 25). These are discussed below.

Status F8h indicates that no relevant information is available because the serial interrupt flag is

not yet set. This occurs between other states and when the controller is not involved in a serial

transfer.

Status 00h indicates that a bus error has occurred during a serial transfer. A bus error is caused

when a START or a STOP condition occurs at an illegal position in the format frame. Examples

of such illegal positions are during the serial transfer of an address Byte, a data Byte, or an

acknowledge bit. When a bus error occurs, SSI is set. To recover from a bus error, the SSSTO

flag must be set and SSI must be cleared. This causes the controller to enter the not addressed

slave mode and to clear the SSSTO flag (no other bits in S1CON are affected). The SDA and

SCL lines are released and no STOP condition is transmitted.

Note:

The TWI controller interfaces to the external TWI bus via 2 port 1 pins: P1.6/SCL (serial clock line)

and P1.7/SDA (serial data line). To avoid low level asserting and conflict on these lines when the

TWI controller is enabled, the output latches of P1.6 and P1.7 must be set to logic 1.

AT89C5132-ROTIL Folha de dados(PDF) 135 Page - ATMEL Corporation