pcf2123 NXP Semiconductors, pcf2123 Datasheet - Page 35

• Manufacturer Part Number: pcf2123
• Description: Spi Real Time Clock/calendar
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCF2123_1
Product data sheet
Fig 24. Serial bus write example
address
counter
SCL
SDI
CE
R/W
b7
xx
0
b6
0
b5
Table 42.
In
10 minutes.
0
In
are not connected together. For this configuration, it is important that pin SDI is never left
floating. It must always be driven either HIGH or LOW. If pin SDI is left open, high I
currents may result. Short transition periods in the order of 200 ns will not cause any
problems.
Bit
7
6 to 4 SA
3 to 0
Figure
Figure
b4
1
b3
Symbol
R/W
0
RA
addr 02
24, the register Seconds is set to 45 seconds and the register Minutes is set to
25, the Months and Years registers are read. In this example, pins SDI and SDO
b2
Command byte definition
0
b1
HEX
1
b0
0
Rev. 01 — 19 November 2008
b7
0
02
Value
0
1
001
0h to Fh
b6
1
seconds data 45
b5
0
b4
0
b3
Description
data read or data write selection
write data
read data
subaddress; other codes will cause the device to ignore
data transfer
register address range
0
BCD
b2
1
b1
0
b0
1
b7
0
03
b6
0
minutes data 10
b5
0
SPI Real time clock/calendar
b4
1
b3
0
BCD
b2
0
PCF2123
© NXP B.V. 2008. All rights reserved.
b1
0
001aaf915
b0
0
04
DD
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