DS1993 Maxim, DS1993 Datasheet - Page 13

• Manufacturer Part Number: DS1993
• Description: The DS1992/DS1993 memory iButtons (hereafter referred to as DS199_) are rugged read/write data carriers that act as a localized database, easily accessible with minimal hardware
• Manufacturer: Maxim

Figure 10. INITIALIZATION PROCEDURE RESET AND PRESENCE PULSE
V
READ/WRITE TIME SLOTS
The definitions of write and read time slots are illustrated in Figure 11. The master driving the data line
low initiates all time slots. The falling edge of the data line synchronizes the DS199x to the master by
triggering a delay circuit in the DS199x. During write time slots, the delay circuit determines when the
DS199x samples the data line. For a read data time slot, if a 0 is to be transmitted, the delay circuit
determines how long the DS199x holds the data line low overriding the 1 generated by the master. If the
data bit is a 1, the iButton leaves the read data time slot unchanged.
Figure 11. READ/WRITE TIMING DIAGRAM
Write-One Time Slot
PULLUP MIN
V
V
PULLUP
V
V
IL MAX
IH MIN
PULLUP MIN
0V
V
V
PULLUP
V
IL MAX
IH MIN
RESISTOR
MASTER
DS199x
0V
RESISTOR
MASTER
"RESET PULSE"
MASTER TX
t
RSTL
t
LOW1
15µs
480 µs ≤ t
480 µs ≤ t
15 µs ≤ t
60 ≤ t
60 µs ≤ t
1 µs ≤ t
1 µs ≤ t
PDL
t
R
PDH
< 240 µs
RSTL
RSTH
MASTER RX "PRESENCE PULSE"
LOW1
REC
SLOT
t
< 60 µs
PDH
60µs
13 of 17
<
Sampling Window
t
<
<
SLOT
< 15 µs
∞
∞
∞
< 120 µs
DS199x
*
**
t
PDL
** Includes recovery time
* In order not to mask interrup signaling
+ t
by other devices on the 10Wire bus t
t
RSTH
R
should always be less than 960 us
t
REC
RSTL
DS1992/DS1993