Rainbow Electronics DS1687 - Manual (Page 24)

DS1685/DS1687
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EXTENDED CONTROL REGISTERS
Two extended control registers are provided to supply controls and status information for the extended
features offered by the DS1685/DS1687. These are designated as extended control registers A and B and
are located in register bank 1, locations 04AH and 04BH, respectively. The functions of the bits within
these registers are described as follows.
EXTENDED CONTROL REGISTER 4A
MSB LSB
BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
VRT2 INCR * * PAB RF WF KF
VRT2 – This status bit gives the condition of the auxiliary battery. It is set to a logic 1 condition when
the external lithium battery is connected to the V
BAUX
. If this bit is read as a logic 0, the external battery
should be replaced.
INCR – Increment-in-Progress status bit. This bit is set to a 1 when an increment to the time/date
registers is in progress and the alarm checks are being made. INCR is set to a 1 at 122ms before the
update cycle starts and is cleared to 0 at the end of each update cycle.
PAB – Power-Active Bar control bit. When this bit is 0, the PWR pin is in the active-low state. When this
bit is 1, the PWR pin is in the high-impedance state. This bit can be written to a logic 1 or 0 by the user. If
either WF and WIE = 1 or KF and KSE = 1, the PAB bit is cleared to 0.
RF – Ram Clear Flag. This bit is set to a logic 1 when a high-to-low transition occurs on the RCLR input
if RCE = 1. The RF bit is cleared by writing it to a logic 0. This bit can also be written to a logic 1 to
force an interrupt condition.
WF – Wake-Up Alarm Flag. This bit is set to 1 when a wake-up alarm condition occurs or when the user
writes it to a 1. WF is cleared by writing it to a 0.
KF – Kickstart Flag. This bit is set to a 1 when a kickstart condition occurs or when the user writes it to a
1. This bit is cleared by writing it to a logic 0.
*Reserved bits. These bits are reserved for future use by Dallas Semiconductor. They can be read and written, but have no affect on operation.