st92f124 STMicroelectronics, st92f124 Datasheet - Page 224

• Manufacturer Part Number: st92f124
• Description: 8/16-bit Single Voltage Flash Mcu Family With Ram, E3 Tmemulated Eeprom, Can 2.0b And J1850 Blpd
• Manufacturer: STMicroelectronics

MULTIPROTOCOL SERIAL COMMUNICATIONS INTERFACE (SCI-M)
MULTIPROTOCOL SERIAL COMMUNICATIONS INTERFACE (Cont’d)
10.5.10.2 DMA
Two DMA channels are associated with the SCI,
for transmit and for receive. These follow the reg-
ister scheme as described in the DMA chapter.
DMA Reception
To perform a DMA transfer in reception mode:
1. Initialize the DMA counter (RDCPR) and DMA
2. Enable DMA by setting the RXD bit in the IDPR
3. DMA transfer is started when data is received
DMA Transmission
To perform a DMA transfer in transmission mode:
1. Initialize the DMA counter (TDCPR) and DMA
2. Enable DMA by setting the TXD bit in the IDPR
3. DMA transfer is started by writing a byte in the
If this byte is the first data byte to be transmitted,
the DMA counter and address registers must be
initialized to begin DMA transmission at the sec-
ond byte. Alternatively, DMA transfer can be start-
ed by writing a dummy byte in the TXBR register.
DMA Interrupts
When DMA is active, the Received Data Pending
and the Transmitter Shift Register Empty interrupt
sources are replaced by the DMA End Of Block re-
ceive and transmit interrupt sources.
Note: To handle DMA transfer correctly in trans-
mission, the BSN bit in the IMR register must be
cleared. This selects the Transmitter Shift Register
Empty event as the DMA interrupt source.
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address (RDAPR) registers
register.
by the SCI.
address (TDAPR) registers.
register.
Transmitter Buffer register (TXBR).
The transfer of the last byte of a DMA data block
will be followed by a DMA End Of Block transmit or
receive interrupt, setting the TXEOB or RXEOB
bit.
A typical Transmission End Of Block interrupt rou-
tine will perform the following actions:
1. Restore the DMA counter register (TDCPR).
2. Restore the DMA address register (TDAPR).
3. Clear the Transmitter Shift Register Empty bit
4. Clear the Transmitter End Of Block (TXEOB)
5. Set the TXD bit in the IDPR register to enable
6. Load the Transmitter Buffer Register (TXBR)
The above procedure handles the case where a
further DMA transfer is to be performed.
Error Interrupt Handling
If an error interrupt occurs while DMA is enabled in
reception mode, DMA transfer is stopped.
To resume DMA transfer, the error interrupt han-
dling routine must clear the corresponding error
flag. In the case of an Overrun error, the routine
must also read the RXBR register.
Character Search Mode with DMA
In Character Search Mode with DMA, when a
character match occurs, this character is not trans-
ferred. DMA continues with the next received char-
acter. To avoid an Overrun error occurring, the
Character Match interrupt service routine must
read the RXBR register.
TXSEM in the S_ISR register to avoid spurious
interrupts.
pending bit in the IMR register.
DMA.
with the next byte to transmit.