MRF24XA_15 Datasheet, PDF (162/258 Pages) Microchip Technology – Low-Power, 2.4 GHz ISM-Band IEEE 802.15.4™ RF

MRF24XA
TABLE 5-13: SECURED FRAME TRANSMISSION (IEEE 802.15.4™ MAC FORMAT)
Steps per each Security Case
#
Processing Step
A
B
C
D
E
1 Host MCU constructs the
frame and loads the buffer.
SecEn = 1
FrameVer =
0x (either)
SecEn = 1
FrameVe =
0x (either)
SecEn = 0
FrameVer =
0x (either)
SecEn = 1
FrameVer =
0x (either)
2 For NWK security
processing, Host MCU
configures:
No NWK layer security.
SECKEY
SECSUITE
SEC*INDX⁽¹⁾
NONCE
SECKEY
SECSUITE
SEC*INDX
NONCE
3 Host MCU triggers security
processing without
sending.
TXENC ← 1
TXENC ← 1
4 Device performs the secu-
rity processing for
NWK layer if TXENC is set.
LENGTH and SECEND-
INDX are updated if MIC
takg is appended. TXSZIF if
size run over 127 bytes.
NWK
layer security
LENGTH,
SECENDINDX
NWK
layer security
LENGTH,
SECENDINDX
5 Host MCU awaits TXENCIF
interrupt, indicating comple-
tion. Device clears TXENC.
TXENCIF ← 1
TXENC ← 0
TXENCIF ← 1
TXENC ← 0
6 For MAC security process-
SECKEY
ing, Host MCU configures:
(+NONCE, if
SAMode is not 11)
(+SECSUITE, if
FRAMEVER=2003)
SECKEY
SECSUITE
SEC*INDX
NONCE
No MAC
security
SECKEY
(+NONCE, if
SAMode is not 11)
(+SECSUITE, if
FRAMEVER=200
3)
7 Host MCU sets DTSM to
inhibit the hardware from
overwriting just configured
SECSUITE, SEC*INDX
and NONCE registers.
DTSM = 0
(=1, if SAMode is
not 11)
DTSM = 1
DTSM = x
DTSM = 0
(=1, if SAMode is
not 11)
8 Host MCU triggers Security
processing and sending.
TXST ← 1
TXST ← 1
TXST ← 1
TXST ← 1
9 If SecEn = 1 and DTSM =
0, then the device config-
SECSUITE
ures the SECSUITE,
SEC*INDX NONCE
—
SEC*INDX and NONCE
registers.
SECSUITE
—
SEC*INDX
NONCE
10 Device performs the secu-
rity processing for MAC
MAC
MAC
—
MAC
layer:
layer security
layer security
layer security
LENGTH is adjusted if MIC LENGTH, if MIC
LENGTH, if
LENGTH, if MIC
tag is appended. TXSZIF if
added
MIC added
added
size runs over 127 bytes.
11 LENGTH is adjusted as
CRC is appended (if
CRCSZ = 1). TXSZIF if size
runs over 127 bytes.
LENGTH, CRC
12 Frame is sent.
TXIF (if no TXSZIF or FRMIF)
TXST ← 0
Note 1: SEC*INDX denotes SECHDRINDX, SECPAYINDX and SECENDINDX.
SecEn = 1
FrameVer =
0x (either)
SECKEY
SECSUITE
SEC*INDX
NONCE
TXENC ← 1
NWK
layer security
LENGTH,
SECENDINDX
TXENCIF ← 1
TXENC ← 0
SECKEY
SECSUITE
SEC*INDX
NONCE
DTSM = 1
TXST ← 1
—
MAC
layer security
LENGTH, if MIC
added
DS70005023C-page 162
Preliminary
 2015 Microchip Technology Inc.