Datasheet

 2012-2018 Microchip Technology Inc. DS20002300C-page 10
MCP7951X/MCP7952X
4.0 SPI BUS OPERATION
The MCP795XX is designed to interface directly with
the Serial Peripheral Interface (SPI) port of many of
today’s popular microcontroller families, including
Microchip’s PIC
®
microcontrollers. It may also interface
with microcontrollers that do not have a built-in SPI port
by using discrete I/O lines programmed properly in
software to match the SPI protocol.
The MCP795XX contains an 8-bit instruction register.
The device is accessed via the SI pin, with data being
clocked in on the rising edge of SCK. The CS
pin must
be low for the entire operation.
Table 4-1 contains a list of the possible instruction
bytes and format for device operation. All instructions,
addresses, and data are transferred MSb first, LSb last.
Data (SI) is sampled on the first rising edge of SCK
after CS
goes low.
TABLE 4-1: INSTRUCTION SET SUMMARY
Instruction Name Instruction Format Description
EEREAD 0000 0011 Read data from EEPROM array beginning at selected address
EEWRITE 0000 0010 Write data to EEPROM array beginning at selected address
EEWRDI 0000 0100 Reset the write enable latch (disable write operations)
EEWREN 0000 0110 Set the write enable latch (enable write operations)
SRREAD 0000 0101 Read STATUS register
SRWRITE 0000 0001 Write STATUS register
READ 0001 0011 Read data from RTCC/SRAM array beginning at selected address
WRITE 0001 0010 Write data to RTCC/SRAM array beginning at selected address
UNLOCK 0001 0100 Unlock the protected EEPROM block for a write operation
IDWRITE 0011 0010 Write data to the protected EEPROM block beginning at selected address
IDREAD 0011 0011 Read data from the protected EEPROM block beginning at the selected
address
CLRRAM 0101 0100 Clear all SRAM data to ‘0’