Rainbow Electronics DS1747P - Manual (Page 2)

DS1747/DS1747P
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PIN DESCRIPTION
A0–A18 – Address Input
CE – Chip Enable
OE – Output Enable
WE – Write Enable
V
CC
– Power Supply Input
GND – Ground
DQ0–DQ7 – Data Input/Output
NC – No Connection
RST – Power–on Reset Output(Power–
Cap Module board only)
X1, X2 – Crystal Connection
V
BAT
– Battery Connection
ORDERING INFORMATION
DS1747P (5V)
blank 32-pin DIP Module
P 34-pin PowerCap Module board*
DS1747WP (3.3V)
blank 32-pin DIP Module
P 34-pin PowerCap Module board*
*DS9034PCX (PowerCap) Required:
(must be ordered separately)
DESCRIPTION
The DS1747 is a full function, year 2000 compliant (Y2KC), real–time clock/calendar (RTC) and 512k
x 8 non–volatile static RAM. User access to all registers within the DS1747 is accomplished with a
bytewide interface as shown in Figure 1. The Real-time clock (RTC) information and control bits reside
in the eight upper most RAM locations. The RTC registers contain century, year, month, date, day,
hours, minutes, and seconds data in 24-hour BCD format. Corrections for the date of each month and
leap year are made automatically. The RTC clock registers are double buffered to avoid access of
incorrect data that can occur during clock update cycles. The double buffered system also prevents time
loss as the timekeeping countdown continues unabated by access to time register data. The DS1747 also
contains its own power–fail circuitry which deselects the device when the V
CC
supply is in an out of
tolerance condition. This feature prevents loss of data from unpredictable system operation brought on
by low V
CC
as errant access and update cycles are avoided.