參數(shù)資料
型號: M37212M4
廠商: Mitsubishi Electric Corporation
英文描述: Single Chip 8 Bits Microcomputer(8位單片機)
中文描述: 單芯片8位單片機(8位單片機)
文件頁數(shù): 37/119頁
文件大?。?/td> 1308K
代理商: M37212M4
37
SINGLE-CHIP 8-BIT CMOS MICROCOMPUTER for VOLTAGE SYNTHESIZER
with ON-SCREEN DISPLAY CONTROLLER
M37212M4/M8–XXXSP, M37212M6–XXXSP/FP
M37212EFSP/FP
MITSUBISHI MICROCOMPUTERS
Rev. 1.0
8.6.5 I
2
C Status Register
The I
2
C status register (address 00D9
16
) controls the I
2
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.
(1) Bit 0: last receive bit (LRB)
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 executing a
write instruction to the I
2
C data shift register (address 00D7
16
).
(2) Bit 1: general call detecting flag (AD0)
This bit is set to “1” when a general call
8
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 condition.
8
General call: The master transmits the general call address “00
16
to all slaves.
(3) Bit 2: slave address comparison flag (AAS)
This flag indicates a comparison result of address data.
I
In the slave receive mode, when the 7-bit addressing format is
selected, this bit is set to “1” in one of the following conditions.
The address data immediately after occurrence of a START con-
dition matches the slave address stored in the high-order 7 bits
of the I
2
C address register (address 00D8
16
).
A general call is received.
I
In the slave reception mode, when the 10-bit addressing format is
selected, this bit is set to “1” with the following condition.
When the address data is compared with the I
2
C address regis-
ter (8 bits consists of slave address and RBW), the first bytes
match.
I
The state of this bit is changed from “1” to “0” by executing a write
instruction to the I
2
C data shift register (address 00D7
16
).
(4) Bit 3: arbitration lost
8
detecting flag (AL)
n 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 re-
ceive and recognize its own slave address transmitted by another
master device.
8
Arbitration lost: The status in which communication as a master is
disabled.
(5) Bit 4: I
2
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
generation is disabled. Figure 8.6.8 shows an interrupt request sig-
nal generating timing chart.
The PIN bit is set to “1” in any one of the following conditions.
Executing a write instruction to the I
2
C data shift register (address
00D7
16
).
When the ESO bit is “0”
At reset
The conditions in which the PIN bit is set to “0” are shown below:
Immediately after completion of 1-byte data transmission (includ-
ing when arbitration lost is detected)
Immediately after completion of 1-byte data reception
In the slave reception mode, with ALS = “0” and immediately after
completion of slave address or general call address reception
In the slave reception mode, with ALS = “1” and immediately after
completion of address data reception
(6) 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 condition
duplication prevention function (See note).
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
ESO bit of the I
2
C control register (address 00DA
16
) is “0” and at
reset, the BB flag is kept in the “0” state.
(7) Bit 6: communication mode specification bit
(transfer direction specification bit: TRX)
This bit decides the direction of transfer for data communication. When
this bit is “0,” the reception mode is selected and the data of a trans-
mitting device is received. When the bit is “1,” the transmission mode
is selected and address data and control data are output into the
SDA in synchronization with the clock generated on the SCL.
When the ALS bit of the I
2
C control register (address 00DA
16
) is “0”
in the slave reception mode is selected, the TRX bit is set to “1”
(transmit) if the least significant bit (R/W bit) of the address data trans-
mitted by the master is “1.” When the ALS bit is “0” and the R/W bit is
“0,” the TRX bit is cleared to “0” (receive).
The TRX bit is cleared to “0” in one of the following conditions.
When arbitration lost is detected.
When a STOP condition is detected.
When occurence of a START condition is disabled by the START
condition duplication prevention function (Note).
With MST = “0” and when a START condition is detected.
With MST = “0” and when ACK non-return is detected.
At reset
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