ATPL230A datasheet(24/122 Pages) ATMEL

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ATPL230A [DATASHEET]

Atmel-43053J-ATPL230A-Datasheet_22-Sep-16

MAC Coprocessor

ATPL230A accelerators can be used to perform PRIME MAC-specific tasks by hardware, decreasing CPU load from

the external MCU/MPU. For that purpose, Cyclic Redundance Check (CRC) and AES128 encryption blocks are

available in ATPL230A.

Please refer to Atmel doc43048 “Atmel PRIME Implementation” for Atmel software package detailed description and

functionality.

8.1

Cyclic Redundancy Check (CRC)

8.1.1

PRIME v1.3 CRC

There are three types of MAC PDUs (generic, promotion and beacon) for different purposes, and each one has its

own specific CRC. There is a hardware implementation of every CRC type calculated by the MAC layer. This CRC

hardware-calculation is enabled by default. Note that the CRC included at the physical layer is also a hardware

implementation available (enabled by default).

Figure 8-1.

Example: Generic MAC PDU format and generic MAC header detail

In transmission all CRC bytes are real-time calculated and the last bytes of the MAC PDU are overwritten with these

values, (provided that the field HT in the first byte of the MAC header in transmission data is equal to the

corresponding MAC PDU type).

In reception the CRC bytes are also real-time calculated and these bytes are checked with the last bytes of the MAC

PDU. If the CRC is not correct, then an error flag is activated, the complete frame is discarded, and the corresponding

error counter is increased. These counters allow the MAC layer to take decisions according to error ratio.

For the Generic MAC PDU

, there is an 8-bit CRC in the Generic MAC header, which corresponds to PRIME

HDR.HCS. In reception, if this CRC doesn’t check successfully, the current frame is discarded and no interruption is

generated.

This works in the same way as CRC for the PHY layer (CRC Ctrl, located in the PHY header, see PRIME specification

for further information).

There is another CRC for the Generic MAC PDU which is the last field of the GPDU. It is 32 bits long and it is used to

detect transmission errors. The CRC shall cover the concatenation of the SNA with the GPDU except for the CRC

field itself. In reception, if the CRC is not successful then an internal flag is set and the error counter is increased.

For the Promotion Needed PDU

there is an 8-bit CRC, calculated with the first 13 bytes of the header. In reception,

if this CRC is not correct, then an internal flag is set and the corresponding error counter is increased.

For the Beacon PDU

there is a 32-bit CRC calculated with the same algorithm as the one defined for the CRC of the

Generic MAC PDU. This CRC shall be calculated over the complete BPDU except for the CRC field itself. In

reception, if this CRC is not successful, then an internal flag is set and the same error counter used for GPDU is

increased. The hardware used for this CRC is the same as the one used for GPDU.

Generic MAC Header

Packet 1

. . .

Packet n

CRC

Unused

HDR.HT

Reserved

HDR.DO

HDR. LEVEL

HDR. HCS

MSB

LSB

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