One-Wire Master Registers
1514
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
1-Wire Master Module
22.5.3 ONEWIREDATW Register (Offset = 0x8) [reset = 0x0]
1-Wire Data Write (ONEWIREDATW), offset 0x008
The 1-Wire Data Write (ONEWIREDATW) and 1-Wire Data Read (ONEWIREDATR) registers are used to
transmit or receive data. Data is processed LSB first, which means the lowest (and possibly only) byte is
transferred first. Note that for normal processor use of writing and write/read, the ONEWIREDATW
register must be written before the OP field of the ONEWIRECS register is programmed. If reading (or
write/read), the ONEWIREDATR register is read after completion (when OP returns to value 0). When
doing write/read ( OP =0x3), either register can be written. Because bits written as a 1 in the
ONEWIREDATR register also act as a read, writing 0xFF is the same as a read of two bytes. Writing 0xF0
allows writing 0 for the lower nibble and reading the upper nibble. If the slave does not know it is a read,
each written 1 reads back as 1.
ONEWIREDATW is shown in
and described in
.
Return to
Figure 22-9. ONEWIREDATW Register
31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10
9
8
7
6
5
4
3
2
1
0
B3
B2
B1
B0
R/W-0x0
R/W-0x0
R/W-0x0
R/W-0x0
Table 22-7. ONEWIREDATW Register Field Descriptions
Bit
Field
Type
Reset
Description
31-24
B3
R/W
0x0
Upper Data Byte. This data byte is used when SZ field = 3.
23-16
B2
R/W
0x0
Upper Middle Data Byte. Contains upper middle data byte and is
used when SZ field = 2 or 3.
15-8
B1
R/W
0x0
Lower Middle Data Byte. Contains lower middle data byte and is
used when SZ field = 1, 2, or 3.
7-0
B0
R/W
0x0
Lowest Data Byte. Contains byte data being read or written
(depending on the operation). This byte is always used.