
7542 Group
Rev.3.02 Oct 31, 2006 Page 50 of 134
REJ03B0006-0302
Bus collision detection (SIO1)
SIO1 can detect a bus collision by setting UART1 bus collision de-
tection interrupt enable bit.
When transmission is started in the clock synchronous or asyn-
chronous (UART) serial I/O mode, the transmit pin TxD
1
is
compared with the receive pin RxD
1
in synchronization with rising
edge of transmit shift clock. If they do not coincide with each other,
a bus collision detection interrupt request occurs.
When a transmit data collision is detected between LSB and MSB
of transmit data in the clock synchronous serial I/O mode or be-
tween the start bit and stop bit of transmit data in UART mode, a
bus collision detection can be performed by both the internal clock
and the external clock.
A block diagram is shown in Fig. 58.
A timing diagram is shown in Fig. 59.
Note: Bus collision detection can be used when SIO1 is operating
at full-duplex communication. When SIO1 is operating at
half-duplex communication, set bus collision detection inter-
rupt to be disabled.
Fig. 58 Block diagram of bus collision detection interrupt circuit
Fig. 59 Timing diagram of bus collision detection interrupt
D
TxD
1
RxD
1
Shift clock
UART1 bus collision detection
interrupt valid bit
(Address 000A
16
, bit 1)
UART1 bus collision detection
interrupt discrimination bit
(Address 000B
16
, bit 1)
Key-on wakeup/
UART1 bus collision detection
interrupt request bit
(Address 003C
16
, bit 6)
Key-on wakeup interrupt request
Q
0 : No interrupt request issued
Interrupt source set register
(INTSET: address 000A
16
, initial value: 00
16
)
Key-on wakeup interrupt valid bit
b7 b0
0: Interrupt invalid
Interrupt source discrimination register
(INTDIS: address 000B
16
, initial value: 00
16
)
Key-on wakeup interrupt discrimination bit
b7 b0
Interrupt request register 1
(IREQ1 : address 003C
16
, initial value : 00
16
)
Serial I/O1 receive interrupt request bit
b7 b0
Serial I/O1 receive interrupt enable bit
0 : Interrupts disabled
Interrupt control register 1
(ICON1 : address 003E
16
, initial value : 00
16
)
b7 b0
1 : Interrupts enabled
CNTR
0
interrupt enable bit
Key-on wake up/UART1 bus collision
INT
1
interrupt enable bit
INT
0
interrupt enable bit
Serial I/O2 transmit interrupt enable bit
Serial I/O2 receive interrupt enable bit
Serial I/O1 transmit interrupt enable bit
detection interrupt enable bit
1 : Interrupt request issued
CNTR
0
interrupt request bit
detection interrupt request bit
Key-on wake up/UART1 bus collision
INT
1
interrupt request bit
INT
0
interrupt request bit
Serial I/O2 transmit interrupt request bit
Serial I/O2 receive interrupt request bit
Serial I/O1 transmit interrupt request bit
1: Interrupt occurs
0: Interrupt does not occur
Not used (returns “0” when read)
Timer 1 interrupt discrimination bit
A/D conversion interrupt discrimination bit
discrimination bit
UART1 bus collision detection interrupt
1: Interrupt valid
Not used (returns “0” when read)
Timer 1 interrupt valid bit
A/D conversion interrupt valid bit
UART1 bus collision detection
interrupt valid bit
Fig. 57 Bus collision detection circuit related registers
Bus collision detection
interrupt generation
Data collision
Transmit shift clock
Transmit pin TxD
1
Receive pin RxD
1