User Manual
628
Rev. 1.1
2019-03-18
TLE984xQX
Microcontroller with LIN and Power Switches for Automotive Applications
UART1/UART2
19.4
Multiprocessor Communication
Modes 2 and 3 have a special provision for multiprocessor communication using a system of address bytes
with bit 9 = 1 and data bytes with bit 9 = 0. In these modes, 9 data bits are received. The 9th data bit goes into
RB8 (SCON.2). The communication always ends with one stop bit. The port can be programmed such that
when the stop bit is received, the serial port interrupt will be activated only if RB8 = 1.
This feature is enabled by setting bit SM2 in register SCON. One of the ways to use this feature in
multiprocessor systems is described in the following paragraph.
When the master processor wants to transmit a block of data to one of several slaves, it first sends out an
address byte that identifies the target slave. An address byte differs from a data byte in the 9th bit. The 9th bit
in an address byte is 1 and in a data byte the 9th bit is 0. With SM2 = 1, no slave will be interrupted by a data
byte. An address byte, however, will interrupt all slaves, so that each slave can examine the received byte and
see if it is being addressed. The addressed slave will clear its SM2 bit and prepare to receive the data bytes that
will be coming. The slaves that were not being addressed retain their SM2 bits as set and ignore the incoming
data bytes.
Note: Bit SM2 has no effect in mode 0. SM2 can be used in mode 1 to check the validity of the stop bit. In a mode
1 reception, if SM2 = 1, the receive interrupt will not be activated unless a valid stop bit is received.
19.5
Interrupts
The two UART interrupts can be separately enabled or disabled by setting or clearing their corresponding
enable bits in SCU SFR MODIEN2. An overview of the UART interrupt sources is shown in
Table 331 UART
Interrupt
Sources
Interrupt
Flag
Interrupt Enable Bit
Reception completed
SCON.RI
SCU_MODIEN2.RIEN1/2
Transmission completed
SCON.TI
SCU_MODIEN2.TIEN1/2