The TXWAKE bit value is placed in the address bit. During transmission, when the SCITXBUF register and TXWAKE are loaded into the TXSHF register and WUT respectively, TXWAKE is reset to 0 and WUT becomes the value of the address bit of the current frame. Thus, to send an address:
- Set the TXWAKE bit to 1 and write the appropriate
address value to the SCITXBUF register.
When
this address value is transferred to the TXSHF
register and shifted out, the address bit is sent
as a 1. This flags the other processors on the
serial link to read the address.
- Write to SCITXBUF and TXWAKE after TXSHF and WUT are loaded. (Can be written to immediately since both TXSHF and WUT are both double-buffered.
- Leave the TXWAKE bit set to 0 to transmit non-address frames in the block.
Note: As a general rule, the address-bit format is
typically used for data frames of 11 bytes or less.
This format adds one bit value (1 for an address
frame, 0 for a data frame) to all data bytes
transmitted. The idle-line format is typically used
for data frames of 12 bytes or more.