
DS2490
15 of 50
1-Wire Bus Speed Codes Table 6
Code
Speed
Data Rate
0x0
Regular
65
μs time slot (15.4kbps)
0x1
Flexible
65
μs to 72μs time slot
(13.9kbps to 15.4kbps)
0x2
Overdrive 10
μs time slot (100kbps)
0x3..0xF
reserved
undefined
STRONG PULLUP DURATION—This command is used to set the time duration of a 1-Wire strong
pullup. As shown in Table 7, the time is controlled with an unsigned 8-bit binary number between 0x00
and 0xFE which specifies the duration in multiples of 16ms. A value of 0x01 specifies 16ms, 0x02 equals
32ms, etc. A value of 0x00 specifies infinite duration. Parameter value 0xFF is reserved and will cause
the device to deliver a pullup duration of <1μs. To terminate an infinite duration pullup use either the
HALT EXECUTION WHEN DONE or HALT EXECUTION WHEN IDLE Control commands as
described in Appendix 1. The DS2490 power-up default strong pullup duration register value is 512ms.
Strong Pullup Duration Codes Table 7
Value
Nominal Strong Pullup Duration
0x00
infinite
0x01
16ms
0x02
32ms
…
0xFE
4.064s
0xFF
reserved
PROG PULSE DURATION—This command is used to set the time duration of a 1-Wire Programming
Pulse. As shown in Table 8, the time is controlled with a an unsigned 8-bit binary number between 0x00
and 0xFE specifying the duration in multiples of 8s. A value of 0x00 stands for infinite duration.
Parameter value 0xFF is reserved and will cause the device to deliver a pulse duration of <1μs. To
terminate an infinite duration programming pulse use the HALT EXECUTION WHEN DONE or HALT
EXECUTION WHEN IDLE command. The DS2490 power-up default strong pullup duration register
value is 512S.
Prog Pulse Duration Codes Table 8
Value
Nominal Prog Pulse Duration
0x00
infinite
0x01
8s
0x02
16s
…
0xFE
2.032ms
0xFF
reserved
PULLDOWN SLEW RATE—This command is used to select the pulldown slew rate for 1-Wire bus
Flexible Speed operation; eight pulldown slew rates are possible. The parameter codes to select the
desired or required slew rate are as listed in Table 9. The slew rate numbers in the table represent nominal