Addr
Data
Addr
S
ta
rt
S
ta
rt
Address frame
(address bit = 1)
Data frame
(address bit = 0)
Idle time
is of no
significance
One block
Several blocks of frames
Data format
(pins SCIRX,
SCITX)
Data format
expanded
S
ta
rt
1
0
1
Idle time is not significant
P
a
ri
ty
S
to
p
P
a
ri
ty
S
to
p
P
a
ri
ty
S
to
p
Idle time
is of no
significance
Address frame
(address bit = 1)
SCI Communication Formats
1331
SPNU503C – March 2018
Copyright © 2018, Texas Instruments Incorporated
Serial Communication Interface (SCI) Module
26.2.4.2 Address-Bit Multiprocessor Mode
In the address-bit protocol, each frame has an extra bit immediately following the data field called an
address bit. A frame with the address bit set to 1 is an address frame; a frame with the address bit set to 0
is a data frame. The idle period timing is irrelevant in this mode.
illustrates the format of
several blocks and frames with the address-bit mode.
When address-bit mode is used, the value of the TXWAKE bit is the value sent as the address bit. To
send an address frame, software must set the TXWAKE bit. This bit is cleared as the contents of the
SCITD are shifted from the TXWAKE register so that all frames sent are data except when the TXWAKE
bit is written as a 1.
No dummy write to SCITD is required before an address frame is sent in address-bit mode. The first byte
written to SCITD after the TXWAKE bit is written to 1 is transmitted with the address bit set when address-
bit mode is used.
Figure 26-5. Address-Bit Multiprocessor Communication Format