One-Wire Master Registers
1512
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
1-Wire Master Module
Table 22-5. ONEWIRECS Register Field Descriptions (continued)
Bit
Field
Type
Reset
Description
9
NOATR
R
0x0
Answer-to-Reset Status. This bit is disabled if the SKATR bit is set.
0x0 = Answer-to-reset behavior was as expected.
0x1 = No answer-to-reset was detected after last reset ( RST =1),
which indicates no slave may be present on the bus.
8
BUSY
R
0x0
Busy Status.
0x0 = No activity on the bus.
0x1 = Activity is taking place on the bus as a result of a reset, read,
write or read/write transaction.Because this bit is on the PIOSC clock
domain, it does not set immediately when a read, write, read/write or
reset transaction begins. The OPC and RST bits in the
ONEWIRERIS register should be used to verify when these
operations have completed.
7
SKATR
R/W
0x0
Skip Answer-to-Reset Enable.
0x0 = No effect.
0x1 = Transaction goes from reset to first byte transfer without an
answer-to-reset (presence detect) after programmed rest period has
passed.
6
LSAM
R/W
0x0
Late Sample Enable. This bit is used for long distance lines or when
the slave cannot pull low quickly.
0x0 = Late sample disabled.
0x1 = 1-Wire module samples late in the read. The sample point
moves to 50 µs for normal and 7 µs for overdrive (versus 16 µs and
2 µs in normal operation).
5
ODRV
R/W
0x0
Overdrive Enable.
0x0 = Overdrive mode disabled.
0x1 = Overdrive mode is enabled.
4-3
SZ
R/W
0x0
Data Operation Size. This field is used to program the size in bytes
of data operations transferred to and from the ONEWIREDATn
registers per request.
0x0 = 1 byte
0x1 = 2 bytes
0x2 = 3 bytes
0x3 = 4 bytes
2-1
OP
R/W
0x0
Operation Request. If written with a non-zero value, this field
requests data operations on the 1-Wire bus for number of bytes
configured by the SZ field. This field does not clear until the
operation completes. The operation starts immediately. If using write
or write/read, the ONEWIREDATW register must be written first.
µDMA operations are handled by the ONEWIREDMA register.
0x0 = No operation
0x1 = Read
0x2 = Write
0x3 = Write/Read
0
RST
R/W
0x0
Reset Request. If RST = 1, a reset operation begins. This bit clears
when the reset operation is complete and the NOATR bit can be
read to verify that a slave responded. If this bit is set at the same
time as the OP bit is set, the reset runs first and the operation starts
when reset has completed. If this bit is written when an operation is
already in progress, it cancels the operation and starts the reset.
0x0 = No effect.
0x1 = Reset operation request.