Direct Access To Serial Pins - Fujitsu MB91460 SERIES FR60 User Manual

Chapter 32 USART (LIN / FIFO)
7.USART Operation
LIN
bus
(SIN)
RXE
LBD
(IRQ0)
LBIE
Internal
Signal
to ICU
IRQ from
ICU
RDRF
(IRQ0)
RIE
Read
RDR
by CPU
Reception Interrupt enable
LIN break detected and Interrupt
IRQ cleared by CPU (LBD -> 0)
IRQ cleared: Begin of Input Capture

7.4 Direct Access to Serial Pins

USART allows the user to access directly the transmission pin (SOT04) or the reception pin (SIN04).
■ USART Direct Pin Access
The USART provides the ability for the user to directly access the serial input or output pin. The software can
always monitor the incoming serial data by reading the SIOP bit of the ESCR04. If setting the Serial Output
Pin direct access Enable (SOPE) bit of the ESCR04 the software can force the SOT04 pin to a desired value.
Note, that this access is only possible, if the transmission shift register is empty (i. e. no transmission activity).
In LIN mode this function can be used for reading back the own transmission and is used for error handling if
something is physically wrong with the single-wire LIN-bus.
(Note) Write the desired value to the SIOP pin before enabling the output pin access, to prevent undesired
peaks. The peaks can occur because SIOP holds the last written value.
During a Read-Modify-Write operation the SIOP bit returns the actual value of the SOT04 pin in the read cycle
instead the value of SIN04 during a normal read instruction.
654
Figure 7-7 LIN bus timing and USART signals
(calibration frame)
old serial clock
LIN break begins
IRQ from ICU
IRQ from ICU
IRQ cleared: Calculate & set new baud rate
LBIE disable
Reception enable
Edge of Start bit of Identifier byte
no clock used
ICU count
Byte read in RDR
RDR read by CPU
new (calibrated) serial clock