DS1390-DS1393 MAXIM [Maxim Integrated Products], DS1390-DS1393 Datasheet - Page 17

• Manufacturer Part Number: DS1390-DS1393
• Description: Low-Voltage SPI/3-Wire RTCs with Trickle Charger
• Manufacturer: MAXIM [Maxim Integrated Products]

The INTCN bit used in the DS1390/DS1393 becomes
the SQW pin-enable bit in the DS1392. This bit powers
up a zero, making SQW active.
Bit 7: Oscillator Stop Flag (OSF). A logic 1 in this bit
indicates that the oscillator has stopped or was
stopped for some time and may be used to judge the
validity of the clock and calendar data. This bit is
edge-triggered and is set to logic 1 when the internal
circuitry senses the oscillator has transitioned from a
normal run state to a STOP condition. The following are
examples of conditions that can cause the OSF bit to
be set:
This bit remains at logic 1 until written to logic 0. This
bit can only be written to logic 0. Attempting to write
OSF to logic 1 leaves the value unchanged.
Bit 6: Alarm Flag (AF). A logic 1 in the AF bit indicates
that the time matched the alarm registers. If the AIE bit
Table 5. Trickle-Charge Register
TCS3
X
X
X
1
1
1
1
1
1
0
EOSC
BIT 7
BIT 7
1) The first time power is applied.
2) The voltage present on V
3) The EOSC bit is turned off.
4) External influences on the crystal (i.e., noise,
OSF
insufficient to support oscillation.
leakage, etc.).
TCS2
X
X
X
0
0
0
0
0
0
0
BIT 6
BIT 6
0
0
TCS1
X
X
X
1
1
1
1
1
1
0
TCS0
X
X
X
0
0
0
0
0
0
0
Low-Voltage SPI/3-Wire RTCs with
BBSQI
BIT 5
BIT 5
CC
0
____________________________________________________________________
and V
DS1
0
1
X
0
1
0
1
0
1
0
BACKUP
BIT 4
BIT 4
RS2
0
DS0
0
1
X
1
0
1
0
1
0
0
is
ROUT1
is logic 1 and the INTCN bit is set to logic 1, the
SQW/INT pin is also asserted. AF is cleared when writ-
ten to logic 0. This bit can only be written to logic 0.
Attempting to write to logic 1 leaves the value
unchanged.
The simplified schematic in Figure 9 shows the basic
components of the trickle charger. The trickle-charge
select (TCS) bits (bits 4 to 7) control the selection of
the trickle charger. To prevent accidental enabling,
only a pattern on 1010 enables the trickle charger. All
other patterns disable the trickle charger. The trickle
charger is disabled when power is first applied. The
diode-select (DS) bits (bits 2 and 3) select whether or
not a diode is connected between V
If DS is 01, no diode is selected or if DS is 10, a diode
is selected. The ROUT bits (bits 0 and 1) select the
value of the resistor connected between V
V
resistor-select (ROUT) bits and the diode selected by
the diode-select (DS) bits.
X
X
0
0
0
1
1
1
1
0
BACKUP
BIT 3
BIT 3
Trickle-Charge Register (0F/8Fh)
RS1
0
ROUT0
. Table 5 shows the resistor selected by the
X
X
0
1
1
0
0
1
1
0
Control Register (0D/8Dh) (DS1392 Only)
Disabled
Disabled
Disabled
No diode, 250 resistor
One diode, 250 resistor
No diode, 2k resistor
One diode, 2k resistor
No diode, 4k resistor
One diode, 4k resistor
Initial default value—disabled
ESQW
BIT 2
BIT 2
Trickle Charger
0
Status Register (0E/8Eh)
FUNCTION
BIT 1
BIT 1
0
0
CC
and V
BIT 0
BIT 0
BACKUP
AIE
CC
AF
and
17
.