M48T18-150PC STMicroelectronics, M48T18-150PC Datasheet - Page 14

• Manufacturer Part Number: M48T18-150PC
• Description: IC, TIMEKEEPER, YY-MM-DD-dd, 8KX8, DIP28
• Manufacturer: STMicroelectronics

Specifications of M48T18-150PC

• Clock Format: HH
• Clock Ic Type: Timekeeper
• Memory Configuration: 8K X 8
• Supply Voltage Range: 4.5V To 5.5V
• Digital Ic Case Style: DIP
• No. Of Pins: 28
• Date Format: YY-MM-DD-dd
• Memory Size: 64Kbit
• Nvram Features: RTC, Internal Battery, XTAL
• Interface Type: Parallel
• Access Time: 150ns
• Memory Case Style: DIP
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Clock operations
3
3.1
3.2
14/31
Clock operations
Reading the clock
Updates to the TIMEKEEPER
prevent reading data in transition. The BiPORT™ TIMEKEEPER cells in the RAM array are
only data registers and not the actual clock counters, so updating the registers can be halted
without disturbing the clock itself.
Updating is halted when a '1' is written to the READ bit, the seventh bit in the control
register. As long as a '1' remains in that position, updating is halted. After a halt is issued,
the registers reflect the count; that is, the day, date, and the time that were current at the
moment the halt command was issued.
All of the TIMEKEEPER registers are updated simultaneously. A halt will not interrupt an
update in progress. Updating is within a second after the bit is reset to a '0.'
Setting the clock
The eighth bit of the control register is the WRITE bit. Setting the WRITE bit to a '1,' like the
READ bit, halts updates to the TIMEKEEPER registers. The user can then load them with
the correct day, date, and time data in 24-hour BCD format (on
WRITE bit to a '0' then transfers the values of all time registers (1FF9h-1FFFh) to the actual
TIMEKEEPER counters and allows normal operation to resume. The FT bit and the bits
marked as '0' in
operation.
See the application note AN923, “TIMEKEEPER
information on century rollover.
Table 5
must be written to '0' to allow for normal TIMEKEEPER and RAM
®
Doc ID 2411 Rev 10
registers should be halted before clock data is read to
®
rolling Into the 21
M48T08, M48T08Y, M48T18
Table
st
5). Resetting the
century” for