MITSUBISHI MICROCOMPUTERS
M37274EFSP
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER with CLOSED CAPTION DECODER
and ON-SCREEN DISPLAY CONTROLLER
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generation is disabled. Figure 57 shows an interrupt request signal
(5) I C Status Register
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The I C status register (address 00F816) controls the I C-BUS inter-
face status. The low-order 4 bits are read-only bits and the high-
order 4 bits can be read out and written to.
generating timing chart.
The PIN bit is set to “1” in any one of the following conditions.
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Executing a write instruction to the I C data shift register (address
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■ Bit 0: Last Receive Bit (LRB)
00F616).
This bit stores the last bit value of received data and can also be
used for ACK receive confirmation. If ACK is returned when an ACK
clock occurs, the LRB bit is set to “0.” If ACK is not returned, this bit
is set to “1.” Except in the ACK mode, the last bit value of received
data is input. The state of this bit is changed from “1” to “0” by execut-
When the ESO bit is “0”
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At reset
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The conditions in which the PIN bit is set to “0” are shown below:
Immediately after completion of 1-byte data transmission (includ-
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ing when arbitration lost is detected)
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ing a write instruction to the I C data shift register (address 00F616).
Immediately after completion of 1-byte data reception
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In the slave reception mode, with ALS = “0” and immediately after
■ Bit 1: General Call Detecting Flag (AD0)
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This bit is set to “1” when a general call✽ whose address data is all “0”
is received in the slave mode. By a general call of the master device,
every slave device receives control data after the general call. The
AD0 bit is set to “0” by detecting the STOP condition or START con-
dition.
completion of slave address or general call address reception
In the slave reception mode, with ALS = “1” and immediately after
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completion of address data reception
■ Bit 5: Bus Busy Flag (BB)
This bit indicates the status of use of the bus system. When this bit is
set to “0,” this bus system is not busy and a START condition can be
generated. When this bit is set to “1,” this bus system is busy and the
occurrence of a START condition is disabled by the START condi-
tion duplication prevention function (Note).
✽General call: The master transmits the general call address “0016”
to all slaves.
■ Bit 2: Slave Address Comparison Flag (AAS)
This flag can be written by software only in the master transmission
mode. In the other modes, this bit is set to “1” by detecting a START
condition and set to “0” by detecting a STOP condition. When the
This flag indicates a comparison result of address data.
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In the slave receive mode, when the 7-bit addressing format is
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selected, this bit is set to “1” in one of the following conditions.
ESO bit of the I C control register (address 00F916) is “0” and at
The address data immediately after occurrence of a START
reset, the BB flag is kept in the “0” state.
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condition matches the slave address stored in the high-order
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7 bits of the I C address register (address 00F716).
A general call is received.
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2 In the slave reception mode, when the 10-bit addressing format is
selected, this bit is set to “1” with the following condition.
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When the address data is compared with the I C address
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register (8 bits consists of slave address and RBW), the first
bytes match.
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The state of this bit is changed from “1” to “0” by executing a write
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instruction to the I C data shift register (address 00F616). ■ Bit 3:
Arbitration Lost✽ Detecting Flag (AL)
In the master transmission mode, when a device other than the mi-
crocomputer sets the SDA to “L,”, arbitration is judged to have been
lost, so that this bit is set to “1.” At the same time, the TRX bit is set to
“0,” so that immediately after transmission of the byte whose arbitra-
tion was lost is completed, the MST bit is set to “0.” When arbitration
is lost during slave address transmission, the TRX bit is set to “0”
and the reception mode is set. Consequently, it becomes possible to
receive and recognize its own slave address transmitted by another
master device.
✽Arbitration lost: The status in which communication as a master is
disabled.
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■ Bit 4: I C-BUS Interface Interrupt Request Bit (PIN)
This bit generates an interrupt request signal. Each time 1-byte data
is transmitted, the state of the PIN bit changes from “1” to “0.” At the
same time, an interrupt request signal is sent to the CPU. The PIN bit
is set to “0” in synchronization with a falling edge of the last clock
(including the ACK clock) of an internal clock and an interrupt re-
quest signal occurs in synchronization with a falling edge of the PIN
bit. When the PIN bit is “0,” the SCL is kept in the “0” state and clock
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RENESAS [ RENESAS TECHNOLOGY CORP ]
