I2C BUS INTERFACE
2
I C BUS INTERFACE (Cont’d)
10.8.6.1 DMA between Peripheral and Register
File
The Transaction Counter registers pair must be in-
itialized with the number of DMA transfers to per-
form and will be decremented after each transac-
tion. The DMA Address register pair must be ini-
tialized with the starting address of the DMA table
in the Memory Space, and it is increased after
each transaction. These two register pairs must be
located between addresses 00h and DFh of the
Register File.
If the DMA transaction is made between the pe-
ripheral and the Register File, one register is
required to hold the DMA Address and one to hold
the DMA transaction counter.
These two registers must be located in the Regis-
ter File:
– the DMA Address Register in the even ad-
dressed register,
10.8.6.3 DMA in Master Receive
To correctly manage the reception of the last byte
when the DMA in Master Receive mode is used,
the following sequence of operations must be per-
formed:
– the DMA Transaction Counter in the following
register (odd address).
They are pointed to by the DMA Transaction
Counter Pointer Register (I2CRDC register in re-
ceiving, I2CTDC register in transmitting) located in
the peripheral register page.
1. The number of data bytes to be received must
be set to the effective number of bytes minus
one byte.
In order to select the DMA transaction with the
Register File, the control bit I2CRDC.RF/MEM in
receiving mode or I2CTDC.RF/MEM in transmit-
ting mode must be set.
2. When the Receiving End Of Block condition
occurs, the I2CCR.STOP bit must be set and
the I2CCR.ACK bit must be reset.
The last byte of the reception sequence can be re-
ceived either using interrupts/polling or using
DMA. If the user wants to receive the last byte us-
ing DMA, the number of bytes to be received must
be set to 1, and the DMA in reception must be re-
enabled (IMR.RXDM bit set) to receive the last
byte. Moreover the Receiving End Of Block inter-
rupt service routine must be designed to recognize
and manage the two different End Of Block situa-
tions (after the first sequence of data bytes and af-
ter the last data byte).
The transaction Counter Register must be initial-
ized with the number of DMA transfers to perform
and will be decremented after each transaction.
The DMA Address Register must be initialized with
the starting address of the DMA table in the Regis-
ter File, and it is increased after each transaction.
These two registers must be located between ad-
dresses 00h and DFh of the Register File.
When the DMA occurs between Peripheral and
Register File, the I2CTDAP register (in transmis-
sion) and the I2CRDAP one (in reception) are not
used.
10.8.6.2 DMA between Peripheral and Memory
Space
If the DMA transaction is made between the pe-
ripheral and Memory, a register pair is required to
hold the DMA Address and another register pair to
hold the DMA Transaction counter. These two
pairs of registers must be located in the Register
File. The DMA Address pair is pointed to by the
DMA Address Pointer Register (I2CRDAP register
in reception, I2CTDAP register in transmission) lo-
cated in the peripheral register page; the DMA
Transaction Counter pair is pointed to by the DMA
Transaction Counter Pointer Register (I2CRDC
register in reception, I2CTDC register in transmis-
sion) located in the peripheral register page.
In order to select the DMA transaction with the
Memory Space, the control bit I2CRDC.RF/MEM
in receiving mode or I2CTDC.RF/MEM in transmit-
ting mode must be reset.
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STMICROELECTRONICS [ ST ]
