AT85C51SND3Bx
Table 92 shows the different peripherals (source or destination) ID number. These num-
bers are used to program the SID and the DID in the DFD.
Table 91. Data Flow Descriptor Content
Byte
Byte
Number
Mnemonic Description
Source Identifier
0
1
SID
DID
See Table 92 for peripheral ID number.
Destination Identifier
See Table 92 for peripheral ID number.
Data Packet Size
Decimal value giving the packet size as 2DPS. DPS takes value from 0 (1-byte
packet size) to 13 (8192-byte packet size).
2
DPS
Packet size is limited to 8192 bytes in case of DPS value greater than 13
3
4
DFSH
DFSL
Data Flow Size
16-bit wide data leading to data flow size from 1 to 216- 1 data packets.
Writing 0x0000 to this field enables continuous data flow.
Table 92. Peripheral ID Number
ID Number
Peripheral
0
C51 RAM
1
USB Controller
Audio Controller 1
Audio Controller 2
PSI Controller
SPI Controller
SIO Controller
Nand Flash Controller
MMC/SD Controller
Reserved
2
3
4
5
6
7
8
9 ≤ n ≤ 14
15
Null Device
CRC Processor
In order to verify integrity of data transferred through the DFC, a CRC calculation can be
enabled using DFCRCEN bit in DFCON. It consists in a 16-bit CRC which is the remain-
der after transfer data (MSB first) is divided by G(X). Polynomial formula is: G(X) = X16
+
X15 + X2 + 1.
CRC16 operates on channel 0 only.
After an hardware reset, the CRC value is 0x0000 but can be set to any initial value by
writing two bytes(1) (MSB first) in the DFCRC register.
At the end of the data flow transfer(2), CRC is available to user by reading two bytes(1)
(MSB first) from the DFCRC register.
Notes: 1. This double write or read sequence can be reset by clearing the CRCEN bit.
2. The CRC value is not reset at start-up of a new data transfer.
Null Device
The null device is used to allow CRC calculation on some data transfer (see
Section “CRC Processor”). When selected as destination, the null device is always
ready and simply acknowledges and discards data coming from the source. When
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ATMEL [ ATMEL ]
