Datasheet

PCF2127AT All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet Rev. 6 — 11 July 2013 16 of 86
NXP Semiconductors
PCF2127AT
Integrated RTC, TCXO and quartz crystal
8.5 General purpose 512 bytes static RAM
The PCF2127AT contains a general purpose 512 bytes static RAM. This integrated SRAM
is battery backed and can therefore be used to store data which is essential for the
application to survive a power outage.
9 bits, RA[8:0], define the RAM address pointer in registers RAM_addr_MSB and
RAM_addr_LSB. The register address pointer increments after each read or write
automatically up to 1Bh and then wraps around to address 00h (see Figure 3 on page 6
).
Data is transferred to or from the RAM by the interface. To write to the RAM, the register
RAM_wrt_cmd, to read from the RAM the register RAM_rd_cmd must be addressed
explicitly.
8.5.1 Register RAM_addr_MSB
8.5.2 Register RAM_addr_LSB
8.5.3 Register RAM_wrt_cmd
8.5.4 Register RAM_rd_cmd
Table 14. RAM_addr_MSB - RAM address MSB register (address 1Ah) bit description
Bit Symbol Description
7 to 1 - unused
0 RA8 RAM address, MSB (9
th
bit)
Table 15. RAM_addr_LSB - RAM address LSB register (address 1Bh) bit description
Bit Symbol Description
7 to 0 RA[7:0] RAM address, LSB (1
st
to 8
th
bit)
Table 16. RAM_wrt_cmd - RAM write command register (address 1Ch) bit description
Bit Symbol Description
7 to 0 - data to be written into RAM
Table 17. RAM_rd_cmd - RAM read command register (address 1Dh) bit description
Bit Symbol Description
7 to 0 - data to be read from RAM