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CHAPTER 15 SERIAL INTERFACE UART2
280
User
’
s Manual U14260EJ3V1UD
Notes 5.
Enabling or disabling the occurrence of the receive completion interrupt (INTSR2) in the case of an
error is affected by the setting of bit 0 (ISEM2) of ASIM2.
6.
Even if MPIEN is cleared to 0, reception is started when the start bit is detected, in order to detect
address (ID) reception. At this time, an error in the receive data is not detected if the multi-processor
appended bit is
“
0
”
. If data
“
1
”
is received by mistake, due to bit slip or other cause, when the multi-
processor appended bit is detected, however, ID reception is detected. Consequently, the error in
the receive data is identified, and the error interrupt signal may be generated and the error flag set.
7.
When bit 7 (POWER2) and bit 5 (RXE2) of ASIM2 have not been set to 1, MPIEN2 cannot be cleared
to 0 (remain 1) even if 0 is written to it.
8.
Before setting ISMD2, clear bit 6 (TXE2) of asynchronous serial interface mode register 2 (ASIM2)
to 0.
Remark
When receiving data in the multi-processor transfer mode, the receive completion interrupt (INTSR2)
occurs, regardless of the value of MPIEN2, if data with the multi-processor appended bit set to
“
1
”
is
received. Usually, this receive data is an address (ID) that indicates the other party of communication.
The subsequent receive data can be ignored and the occurrence of an unnecessary receive completion
interrupt (INTSR2) can be disabled by comparing this received ID with the ID of the microcontroller
(for which software processing is necessary) and clearing MPIEN2 if the two IDs do not match.
(7) Port mode register 3 (PM3)
PM3 is a register that sets the input/output of port 3 in 1-bit units.
To use the P34/TxD2/SI3 pin as a serial data output, set PM34 and the output latch of P34 to 0.
To use the P35/RxD2/SO3 pin as a serial data input, and the P36/ASCK2/SCK3 pin as a clock input, set PM35
and PM36 to 1. At this time, the output latches of P35 and P36 can be either 0 or 1.
PM3 is set by a 1-bit or 8-bit memory manipulation instruction.
RESET input sets PM3 to FFH.
Figure 15-9. Format of Port Mode Register 3 (PM3)
Address: FF23H After reset: FFH R/W
Symbol
7
6
5
4
3
2
1
0
PM3
1
PM36
PM35
PM34
PM33
PM32
PM31
PM30
PM3n
I/O mode selection of P3n pin (n = 0 to 6)
0
Output mode (output buffer on)
1
Input mode (output buffer off)