Datasheet

3-Wire Serial-Data Bus
The DS1392/DS1393 provide a 3-wire serial-data bus,
and support both single-byte and multiple-byte data trans-
fers for maximum flexibility. The I/O pin is the serial-data
input/output pin. The CE input is used to initiate and termi-
nate a data transfer. The SCLK pin is used to synchronize
data movement between the master (microcontroller) and
the slave (DS1392/DS1393) devices. Input data is latched
on the SCLK rising edge and output data is shifted out
on the SCLK falling edge. There is one clock for each
bit transferred. Address and data bits are transferred in
groups of eight. Address and data bytes are shifted LSB
first into the I/O pin. Data is transferred out LSB first on
the I/O pin for a read operation.
The address byte is always the first byte entered after CE
is driven high. The MSB (W/R) of this byte determines if
a read or write takes place. If W/R is 0, one or more read
cycles occur. If W/R is 1, one or more write cycles occur.
Data transfers can be one byte at a time or in multiple-
byte burst mode. After CE is driven high, an address is
written to the DS1392/DS1393. After the address, one
or more data bytes can be written or read. For a single-
byte transfer, one byte is read or written and then CE is
driven low (Figures 13 and 14). For a multiple-byte trans-
fer, however, multiple bytes can be read or written after
the address has been written (Figure 15). Each read or
write cycle causes the RTC register address to automati-
cally increment. Incrementing continues until the device is
disabled. The address wraps to 00h after incrementing to
0Fh (during a read) and wraps to 80h after incrementing
to 8Fh (during a write). Note, however, that an updated
copy of the time is only loaded into the user-accessible
copy upon the rising edge of CE. Reading the RTC
registers in a continuous loop does not show the time
advancing.
Figure 15. 3-Wire Multiple-Byte Burst Transfer
CE
SCLK
I/O
ADDRESS
BYTE
DATA
BYTE 0
DATA
BYTE 1
DATA
BYTE N
www.maximintegrated.com
Maxim Integrated │ 24
DS1390–DS1394 Low-Voltage SPI/3-Wire RTCs
with Trickle Charger
Chip Information
TRANSISTOR COUNT: 11,525
PROCESS: CMOS
SUBSTRATE CONNECTED TO GROUND
Thermal Information
Theta-JA: 180°C/W
Theta-JC: 41.9°C/W