M48T18-100MH1 STMicroelectronics, M48T18-100MH1 Datasheet - Page 15

• Manufacturer Part Number: M48T18-100MH1
• Description: RAM Miscellaneous 8KX8 TIMEKEEP 100NS
• Manufacturer: STMicroelectronics

Specifications of M48T18-100MH1

• Bus Type: Parallel
• Date Format: DW:DM:M:Y
• Time Format: HH:MM:SS
• User Ram: 8KB
• Operating Supply Voltage (typ): 5V
• Package Type: SOH
• Operating Supply Voltage (max): 5.5V
• Operating Supply Voltage (min): 4.5V
• Operating Temperature Classification: Commercial
• Operating Temperature (max): 70C
• Operating Temperature (min): 0C
• Pin Count: 28
• Mounting: Surface Mount
• Lead Free Status / Rohs Status: Not Compliant

M48T08, M48T08Y, M48T18
3.3
Note:
3.4
Table 5.
Keys:
Stopping and starting the oscillator
The oscillator may be stopped at any time. If the device is going to spend a significant
amount of time on the shelf, the oscillator can be turned off to minimize current drain on the
battery. The STOP bit (ST) is the MSB of the seconds register. Setting it to a '1' stops the
oscillator. The M48T08/18/08Y (in the PCDIP28 package) is shipped from
STMicroelectronics with the STOP bit set to a '1.' When reset to a '0,' the M48T08/18/08Y
oscillator starts within one second.
To guarantee oscillator startup after initial power-up, first write the STOP bit (ST) to '1,' then
reset to '0.'
Calibrating the clock
The M48T08/18/08Y is driven by a quartz-controlled oscillator with a nominal frequency of
32,768 Hz. A typical M48T08/18/08Y is accurate within 1 minute per month at 25 °C without
calibration. The devices are tested not to exceed ± 35 ppm (parts per million) oscillator
frequency error at 25 °C, which equates to about ±1.53 minutes per month. With the
calibration bits properly set, the accuracy of each M48T08/18/08Y improves to better than
+1/–2 ppm at 25 °C.
The oscillation rate of any crystal changes with temperature.
frequency error that can be expected at various temperatures. Most clock chips compensate
for crystal frequency and temperature shift error with cumbersome “trim” capacitors. The
Address
1FFFh
1FFEh
1FFDh
1FFCh
1FFBh
1FFAh
1FF9h
1FF8h
S = SIGN bit
FT = FREQUENCY TEST bit (set to '0' for normal clock operation)
R = READ bit
W = WRITE bit
ST = STOP bit
0 = Must be set to '0'
Register map
D7
ST
W
0
0
0
0
0
D6
FT
R
10 years
0
0
0
10 seconds
10 minutes
D5
S
0
0
10 hours
10 date
Doc ID 2411 Rev 10
10 M
D4
0
Data
D3
0
Calibration
D2
Seconds
Minutes
Month
Hours
Date
Year
Day
D1
Figure 8 on page 17
D0
Seconds
Minutes
Control
Month
Hours
Date
Year
Day
Function/range
BCD format
Clock operations
shows the
00-99
01-12
01-31
01-07
00-23
00-59
00-59
15/31