M48T58Y-70MH1F STMicroelectronics, M48T58Y-70MH1F Datasheet - Page 16

• Manufacturer Part Number: M48T58Y-70MH1F
• Description: IC TIMEKPR SRAM 64KBIT 5V 28SOIC
• Manufacturer: STMicroelectronics
• Series: Timekeeper®r
• Type: Clock/Calendar/NVSRAMr

Specifications of M48T58Y-70MH1F

• Memory Size: 64K (8K x 8)
• Time Format: HH:MM:SS (24 hr)
• Date Format: YY-MM-DD-dd
• Interface: Parallel
• Voltage - Supply: 4.5 V ~ 5.5 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 28-SOIC, 28-SOH (8.48mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-4722-2

Clock operations
Note:
6.4
16/33
Table 5.
Keys:
When CEB is set to '1,' CB will toggle from '0' to '1' or from '1' to '0' at the turn of the century
(dependent upon the initial value set).
When CEB is set to '0,' CB will not toggle. The WRITE bit does not need to be set to write to
CEB.
Calibrating the clock
The M48T58/Y is driven by a quartz-controlled oscillator with a nominal frequency of 32,768
Hz. 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 M48T58/Y improves to better than +1/–2 ppm at 25°C.
The oscillation rate of any crystal changes with temperature (see
Most clock chips compensate for crystal frequency and temperature shift error with
cumbersome “trim” capacitors. The M48T58/Y design, however, employs periodic counter
correction. The calibration circuit adds or subtracts counts from the oscillator divider circuit
at the divide by 256 stage, as shown in
are blanked (subtracted, negative calibration) or split (added, positive calibration) depends
upon the value loaded into the five calibration bits found in the control register. Adding
counts speeds the clock up, subtracting counts slows the clock down.
The calibration byte occupies the five lower order bits (D4-D0) in the control register 1FF8h.
These bits can be set to represent any value between 0 and 31 in binary form. Bit D5 is the
Address
1FFDh
1FFCh
1FFFh
1FFEh
1FFBh
1FFAh
1FF9h
1FF8h
S = SIGN bit
FT = FREQUENCY TEST bit
R = READ bit
W = WRITE bit
ST = STOP bit
0 = Must be set to '0'
BLE = Battery low enable bit
BL = Battery low bit (read only)
CEB = Century enable bit
CB = Century bit
BLE
ST
D7
Register map
W
0
0
0
0
D6
BL
FT
R
10 Years
0
0
10 seconds
10 minutes
CEB
D5
S
0
10 hours
10 date
Doc ID 2412 Rev 7
10 M
CB
D4
Data
Figure 9 on page
D3
0
Calibration
D2
Seconds
Minutes
Month
Hours
Date
Year
Day
D1
18. The number of times pulses
D0
Figure 8 on page
Century/day
Seconds
Minutes
Control
Month
Hours
Date
Year
Function/range
M48T58, M48T58Y
BCD format
0-1/1-7
00-99
01-12
01-31
00-23
00-59
00-59
18).