Rainbow Electronics DS1305 - Manual (Page 2)

DS1305
2 of 20
PIN DESCRIPTION
V
CC1
- Primary Power Supply
V
CC2
- Backup Power Supply
V
BAT
- +3V Battery Input
V
CCIF
- Interface Logic Power-Supply Input
GND - Ground
X1, X2 - 32,768kHz Crystal Connection
INT0 - Interrupt 0 Output
INT1 - Interrupt 1 Output
SDI - Serial Data In
SDO - Serial Data Out
CE - Chip Enable
SCLK - Serial Clock
SERMODE - Serial Interface Mode
PF - Power-Fail Output
DESCRIPTION
The DS1305 serial alarm real-time clock provides a full binary coded decimal (BCD) clock calendar that
is accessed by a simple serial interface. The clock/calendar provides seconds, minutes, hours, day, date,
month, and year information. The end of the month date is automatically adjusted for months with fewer
than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour
format with AM/PM indicator. In addition, 96 bytes of NV RAM are provided for data storage.
An interface logic power-supply input pin (V
CCIF
) allows the DS1305 to drive SDO and PF pins to a level
that is compatible with the interface logic. This allows an easy interface to 3V logic in mixed supply
systems.
The DS1305 offers dual-power supplies as well as a battery input pin. The dual power supplies support a
programmable trickle charge circuit that allows a rechargeable energy source (such as a super cap or
rechargeable battery) to be used for a backup supply. The V
BAT
pin allows the device to be backed up by
a non-rechargeable battery. The DS1305 is fully operational from 2.0V to 5.5V.
Two programmable time-of-day alarms are provided by the DS1305. Each alarm can generate an
interrupt on a programmable combination of seconds, minutes, hours, and day. “Don’t care” states can be
inserted into one or more fields if it is desired for them to be ignored for the alarm condition. The time-of-
day alarms can be programmed to assert two different interrupt outputs or to assert one common interrupt
output. Both interrupt outputs operate when the device is powered by V
CC1
, V
CC2
, or V
BAT
.
The DS1305 supports a direct interface to SPI serial data ports or standard 3-wire interface. A
straightforward address and data format is implemented in which data transfers can occur 1 byte at a time
or in multiple-byte-burst mode.