SLAZ098AA October 2012 – May 2021 CC430F6125
RF1A Module
Functional
Extra Byte Transmitted in TX
If a transmission is aborted (exits TX mode) during the transmission of the first half of any byte, there will be a repetition of the first byte in the next transmission. This issue is caused by a state machine controlling the mod_rd_data signal in the modulator. This signal asserts at the start of transmission of each full byte, then deasserts after half the byte has been transmitted. If the transmission is aborted after a byte has started but before half the byte is transmitted this signal remains asserted and the first byte in the next transmission is repeated.
As long as the packet handling features of the CC430 are used, this is not a problem since the chip always exits TX mode after the transmission of the last bit in the last byte of the packet. If, however, one disables the packet handling features (MDMCFG2.SYNC_MODE=0) and wants to exit TX mode manually by strobing IDLE, one should make sure that the IDLE strobe is being issued after clocking out 12 dummy bits (8 dummy bits are necessary due to the TX latency, but since this would mean that transmission is aborted within the first half of a byte, 4 extra bits are added).