Texas Instruments CC112 Series, User Manual, Page: 47 / 109

CC112X/CC1175
SWRU295C Page 47 of 108
when
PKT_CFG1.BYTE_SWAP_EN = 1
, the user should swap the address manually in the
DEV_ADDR
register in order to match the received address due to the fact that the packet engine
compares the address register to the received address before the swapping is done.
Figure 19 shows the data sent over the air vs. the data written to the TX FIFO when byte swap is
enabled (assume that whitening and CRC calculation are disabled). If the receiver uses address
filtering, the address should be programmed to be 0xEA.
0 0 0 0 0 0 1 1 0 1 0 1 0 1 1 1 0 0 1 0 0 1 1 0 1 0 1 1 0 0 1 0
0x03 0x57 0x26 0xB2
1 1 0 0 0 0 0 0 1 1 1 0 1 0 1 0 0 1 1 0 0 1 0 0 0 1 0 0 1 1 0 1
0xC0 0xEA 0x64 0x4D
Data written to TX FIFO
Data sent on the air
Figure 19: Data Byte Swap
7.1.8 UART Mode
If UART mode is enabled (
PKT_CFG0.UART_MODE_EN = 1
), the packet engine inserts and removes
start/stop bits automatically. In this mode the packet engine will emulate UART back-to-back
transmissions typically done over an asynchronous RF interface, to enable communication with
simple RF devices without packet support.
The start and stop bits are not handled as data, only inserted/removed in the data stream to/from the
modem, hence all packet features are available in this mode. The value of the start/stop bits is
configurable through the
PKT_CFG0.UART_SWAP_EN
register field.
If whitening is enabled, only the data bits are affected, not the start/stop bits.
A "framing error" occurs in RX mode when the designated "start" and "stop" bits are not received as
expected. As the "start" bit is used to identify the beginning of an incoming byte it acts as a reference
for the remaining bits. If the "start" and "stop" bits are not in their expected value, it means that the
data is not in line and a framing error will occur (the
UART_FRAMING_ERROR
signal will be asserted).
Framing errors will not stop the on-going reception.