CC112X/CC1175
SWRU295C
Page 16 of 108
Both FIFO data and pointers are readable and writeable to enable e.g. re-transmissions, partial flush,
partial readouts, changing only the sequence number before re-transmission etc. Figure 6 shows how
the TX FIFO pointer changes as the FIFO is written and as data are sent on the air (assume variable
packet length mode
PKT_CFG0.LENGTH_CONFIG = 01b
.
0
1
2
3
4
5
6
7
8
9
10
126 127
1
D
0
2
3
x
x
D
1
D
2
D
3
D
4
D
5
x
x
TXFIRST
TXLAST
NUM_TXBYTES = 0x09
STX:
0
1
2
3
4
5
6
7
8
9
10
126 127
1
D
0
2
3
x
x
D
1
D
2
D
3
D
4
D
5
x
x
TXFIRST
TXLAST
NUM_TXBYTES = 0x07
1
D
0
transmitted on the air
STX:
transmitted on the air
2
D
1
D
2
0
1
2
3
4
5
6
7
8
9
10
126 127
1
D
0
2
3
x
x
D
1
D
2
D
3
D
4
D
5
x
x
TXFIRST
TXLAST
NUM_TXBYTES = 0x04
STX:
transmitted on the air
3
D
3
D
4
D
5
0
1
2
3
4
5
6
7
8
9
10
126 127
1
D
0
2
3
x
x
D
1
D
2
D
3
D
4
D
5
x
x
TXFIRST
TXLAST
NUM_TXBYTES = 0x00
Figure 6: FIFO Pointers (TX FIFO)
To transmit packet number 3 over again one can simply write 0x05 to the
TXFIRST
register and then
strobe
STX
again.
In RX mode, when the RX FIFO is empty (i.e.
) the first byte received will not be
available to be read from the RXFIFO using direct FIFO access. Please see Figure 7 (it is assumed
that the receiver uses variable packet length mode (
PKT_CFG0.LENGTH_CFG = 01
) and that
append status is disabled (
) for this example).