ST90158 - MULTIPROTOCOL SERIAL COMMUNICATIONS INTERFACE (SCI-M)
MULTIPROTOCOL SERIAL COMMUNICATIONS INTERFACE (Cont’d)
INTERRUPT/DMA PRIORITY REGISTER (IDPR)
R249 - Read/Write
mat. If software does not reset SB before the min-
imum break length has finished, the break condi-
tion will continue until software resets SB. The SCI
terminates the break condition with a high level on
the transmitter data output for one transmission
clock period.
Reset value: undefined
7
0
AMEN
SB SA RXD TXD
PRL2
PRL1
PRL0
Bit 5 = SA: Set Address.
If an address/9th data bit mode is selected, SA val-
ue will be loaded for transmission into the Shift
Register. This bit is cleared by hardware after its
load.
0: Indicate it is not an address word.
1: Indicate an address word.
Bit 7 = AMEN: Address Mode Enable.
This bit, together with the AM bit (in the CHCR reg-
ister), decodes the desired addressing/9th data
bit/character match operation.
In Address mode the SCI monitors the input serial
data until its address is detected
Note: Proper procedure would be, when the
Transmitter Buffer Register is empty, to load the
value of SA and then load the data into the Trans-
mitter Buffer Register.
AMEN AM
0
0
0
1
Address interrupt if 9th data bit = 1
Address interrupt if character match
Bit 4 = RXD: Receiver DMA Mask.
Address interrupt if character match
and 9th data bit =1
This bit is reset by hardware when the transaction
counter value decrements to zero. At that time a
receiver End of Block interrupt can occur.
0: Disable Receiver DMA request (the RXDP bit in
the S_ISR register can request an interrupt).
1: Enable Receiver DMA request (the RXDP bit in
the S_ISR register can request a DMA transfer).
1
1
0
1
Address interrupt if character match
with word immediately following Break
Note: Upon reception of address, the RXAP bit (in
the Interrupt Status Register) is set and an inter-
rupt cycle can begin. The address character will
not be transferred into the Receiver Buffer Regis-
ter but all data following the matched SCI address
and preceding the next address word will be trans-
ferred to the Receiver Buffer Register and the
proper interrupts updated. If the address does not
match, all data following this unmatched address
will not be transferred to the Receiver Buffer Reg-
ister.
Bit 3 = TXD: Transmitter DMA Mask.
This bit is reset by hardware when the transaction
counter value decrements to zero. At that time a
transmitter End Of Block interrupt can occur.
0: Disable Transmitter DMA request (TXBEM or
TXSEM bits in S_ISR can request an interrupt).
1: Enable Transmitter DMA request (TXBEM or
TXSEM bits in S_ISR can request a DMA trans-
fer).
In any of the cases the RXAP bit must be reset by
software before the next word is transferred into
the Buffer Register.
Bit 2:0 = PRL[2:0]: SCI Interrupt/DMA Priority bits.
The priority for the SCI is encoded with
(PRL2,PRL1,PRL0). Priority level 0 is the highest,
while level 7 represents no priority.
When AMEN is reset and AM is set, a useful char-
acter search function is performed. This allows the
SCI to generate an interrupt whenever a specific
character is encountered (e.g. Carriage Return).
When the user has defined a priority level for the
SCI, priorities within the SCI are hardware defined.
These SCI internal priorities are:
Bit 6 = SB: Set Break.
0: Stop the break transmission after minimum
Receiver DMA request
Transmitter DMA request
Receiver interrupt
highest priority
break length.
1: Transmit a break following the transmission of all
data in the Transmitter Shift Register and the
Buffer Register.
Transmitter interrupt
lowest priority
Note: The break will be a low level on the transmit-
ter data output for at least one complete word for-
164/199
9
ETC [ ETC ]
