PCF2127AT datasheet(17/100 Pages) PHILIPS

17 / 100 page

PCF2127

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Product data sheet

Rev. 8 — 19 December 2014

17 of 100

NXP Semiconductors

PCF2127

Accurate RTC with integrated quartz crystal for industrial applications

8.5.5 Operation examples

8.5.5.1

Writing to the RAM

1. Set RAM address:

– Select register RAM_addr_MSB (send address 1Ah).

– Set value for bit RA8 (data byte of register 1Ah).

Note: register address will be incremented automatically to 1Bh.

– Set value for array RA[7:0] (data byte of register 1Bh).

2. Send RAM write command:

– Select register RAM_wrt_cmd (send address 1Ch).

3. Write data into the RAM:

– Write n data byte into RAM.

For details, see Figure 46 on page 69.

8.5.5.2

Reading from the RAM

1. Set RAM address:

– Select register RAM_addr_MSB (send address 1Ah).

– Set value for bit RA8 (data byte of register 1Ah).

Note: register address will be incremented automatically to 1Bh.

– Set value for array RA[7:0] (data byte of register 1Bh).

2. Send RAM read command:

– Select register RAM_rd_cmd (send address 1Dh).

3. Read from the RAM:

– Read n data byte from the RAM.

For details, see Figure 47 on page 70.

8.6 Power management functions

The PCF2127 has two power supplies:

VDD — the main power supply

VBAT — the battery backup supply

Internally, the PCF2127 is operating with the internal operating voltage Voper(int) which is

also available as VBBS on the battery backed output voltage pin, BBS. Depending on the

condition of the main power supply and the selected power management function,

Voper(int) is either on the potential of VDD or VBAT (see Section 8.6.4).

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