Functional Description
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3-27
3
I
2
C Current Address Read
The I
2
C slave device should maintain the last address accessed during the
last I
2
C read or write operation, incremented by one. The first step in the
programming sequence should be to test the i2_cmplt bit for the operation-
complete status. The next step is to initiate a start sequence by first setting
the i2_start and i2_enbl bits in the I
2
C Control Register and then writing
the device address (bits 7-1) and read bit (bit 0=1) to the I
2
C Transmitter
Data Register. The i2_cmplt bit will be automatically clear with the write
cycle to the I
2
C Transmitter Data Register. The I
2
C Status Register must
now be polled to test the i2_cmplt and i2_ackin bits. The i2_cmplt bit
becomes set when the device address and read bit have been transmitted,
and the i2_ackin bit provides status as to whether or not a slave device
acknowledged the device address. With the successful transmission of the
device address, the I
2
C master controller writes a dummy value
(data=don’t care) to the I
2
C Transmitter Data Register.This causes the I
2
C
master controller to initiate a read transmission from the slave device.
Again, i2_cmplt bit must be tested for proper response. After the I
2
C
master controller has received a byte of data (indicated by i2_datin=1 in
the I
2
C Status Register), the system software may then read the data by
polling the I
2
C Receiver Data Register. The I
2
C master controller does not
acknowledge the read data for a single byte transmission on the I
2
C bus,
but must complete the transmission by sending a stop sequence to the slave
device. This can be accomplished by first setting the i2_stop and i2_enbl
bits in the I
2
C Control Register and then writing a dummy data (data=don’t
care) to the I
2
C Transmitter Data Register. The I
2
C Status Register must
now be polled to test i2_cmplt bit for the operation-complete status. The
stop sequence will relinquish the ASIC master’s possession of the I
2
C bus.
shows the suggested software flow diagram for programming
the I
2
C current address read operation.
Содержание MVME5100 Series
Страница 1: ...MVME5100 Single Board Computer Programmer s Reference Guide V5100A PG2 September 2001 Edition ...
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Страница 62: ...1 34 Computer Group Literature Center Web Site Product Data and Memory Maps 1 ...
Страница 278: ...3 88 Computer Group Literature Center Web Site System Memory Controller SMC 3 ...
Страница 288: ...4 10 Computer Group Literature Center Web Site Hawk Programming Details 4 ...
Страница 320: ...Index IN 12 Computer Group Literature Center Web Site I N D E X ...