參數(shù)資料
型號: ST72651R6
英文描述: SODIMM MEMORY MODULE, 64MB, INDUSTRIAL TEMP
中文描述: ST7的-低功耗。全速USB 8位32K快閃微控制器。 5K內存。閃存卡的I /樓計時器。脈寬調制。 ADC的。的I2C
文件頁數(shù): 15/166頁
文件大?。?/td> 2089K
代理商: ST72651R6
ST7265x
111/166
IC SINGLE MASTER BUS INTERFACE (Cont’d)
11.7.4 Functional Description (Master Mode)
Refer to the CR, SR1 and SR2 registers in Section
11.7.7. for the bit definitions.
By default the I2C interface operates in idle mode
(M/IDL bit is cleared) except when it initiates a
transmit or receive sequence.
To switch from default idle mode to Master mode a
Start condition generation is needed.
Start condition and Transmit Slave address
Setting the START bit causes the interface to
switch to Master mode (M/IDL bit set) and genera-
tes a Start condition.
Once the Start condition is sent:
– The EVF and SB bits are set by hardware with
an interrupt if the ITE bit is set.
Then the master waits for a read of the SR1 regis-
ter followed by a write in the DR register with the
Slave address byte, holding the SCL line low
(see Figure 68 Transfer sequencing EV1).
Then the slave address byte is sent to the SDA
line via the internal shift register.
After completion of this transfer (and acknowledge
from the slave if the ACK bit is set):
– The EVF bit is set by hardware with interrupt
generation if the ITE bit is set.
Then the master waits for a read of the SR1 regis-
ter followed by a write in the CR register (for exam-
ple set PE bit), holding the SCL line low (see Fi-
gure 68 Transfer sequencing EV2).
Next the master must enter Receiver or Transmit-
ter mode.
Master Receiver
Following the address transmission and after SR1
and CR registers have been accessed, the master
receives bytes from the SDA line into the DR regis-
ter via the internal shift register. After each byte
the interface generates in sequence:
– Acknowledge pulse if if the ACK bit is set
– EVF and BTF bits are set by hardware with an in-
terrupt if the ITE bit is set.
Then the interface waits for a read of the SR1 re-
gister followed by a read of the DR register, hol-
ding the SCL line low (see Figure 68 Transfer se-
quencing EV3).
To close the communication: before reading the
last byte from the DR register, set the STOP bit to
generate the Stop condition. The interface goes
automatically back to idle mode (M/IDL bit clea-
red).
Note: In order to generate the non-acknowledge
pulse after the last received data byte, the ACK bit
must be cleared just before reading the second
last data byte.
Master Transmitter
Following the address transmission and after SR1
register has been read, the master sends bytes
from the DR register to the SDA line via the inter-
nal shift register.
The master waits for a read of the SR1 register fol-
lowed by a write in the DR register, holding the
SCL line low (see Figure 68 Transfer sequencing
EV4).
When the acknowledge bit is received, the
interface sets:
– EVF and BTF bits with an interrupt if the ITE bit
is set.
To close the communication: after writing the last
byte to the DR register, set the STOP bit to gene-
rate the Stop condition. The interface goes auto-
matically back to idle mode (M/IDL bit cleared).
Error Case
– AF: Detection of a non-acknowledge bit. In this
case, the EVF and AF bits are set by hardware
with an interrupt if the ITE bit is set. To resume,
set the START or STOP bit.
Note: The SCL line is not held low.
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