Direct Access To Serial Pins - Fujitsu MB90390 Series Hardware Manual

CHAPTER 20 UART2, UART3
20.7.4

Direct Access to Serial Pins

UART2, UART3 allows the user to directly access to the transmission pin (SOT2, SOT3)
or the reception pin (SIN2, SIN3).
■ UART2, UART3 Direct Pin Access
The UART2, UART3 provides the ability for the software to access directly to serial input or output pin.
The states of serial input pins (SIN2/SIN3) can be read via the serial I/O pin direct access bits (ESCR2/
ESCR3:SIOP).
You can set the values of the serial output pins (SOT2/SOT3) arbitrarily by enabling direct write (ESCR2/
ESCR3:SOPE=1) to the serial output pins (SOT2/SOT3), writing "0" or "1" to the serial I/O pin direct
access bits (ESCR2/ESCR3:SIOP), and enabling serial output (SMR2/SMR3:SOE=1).
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.
Notes:
• That this access is only possible, if the transmission shift register is empty (i. e. no transmission
activity).
• Write the desired value to the SIOP pin before enabling the output pin access to prevent
undesired output level because SIOP holds the last written value.
• During a Read-Modify-Write operation the SIOP bit returns the actual value of the SOT2/SOT3 pin
in the read cycle instead of the value of SIN2/SIN3 during a normal read instruction.
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