MB85RQ4MLPF-G Datasheet, PDF (11/36 Pages) Fujitsu Component Limited. – 4 M (512 K × 8) Bit Quad SPI

MB85RQ4ML
• FSTRD
The FSTRD command reads FRAM memory cell array data. After driving CS low, FSTRD op-code and a
arbitrary 24 address bits are input to SI, followed by 8 mode bits. The 5 upper address bits are ignored.
Then, 8 clock cycles are input to SCK. SO outputs 8 data bits synchronously to the falling edge of SCK.
While reading, the SI value is invalid. When CS is risen, the FSTRD command is completed, otherwise it
keeps on reading with automatic address increment which is enabled by continuously sending clocks to SCK
in unit of 8 cycles before CS rising. When it reaches the most significant address, it rolls over to the starting
address, and reading cycle keeps on infinitely. The maximum clock frequency for the FSTRD command is
108 MHz.
Address jumps can be done without the need for additional FSTRD command. This is controlled through
the setting of the Mode bits after the address sequence. This added feature, which is called “XIP mode”,
removes the need for the command sequence. If the Mode bits equal EFH or AFH, then the device remains
in FSTRD mode and the next address can be entered (after CS is raised high and then asserted low) without
requiring the FSTRD command, thus eliminating 8 cycles for the command sequence. If the Mode bits are
any value other than EFH and AFH, then the next time CS is raised high the device will be released from
FSTRD mode. After that, the device can accept SPI commands. CS should not be driven high during mode
bits as this may make the mode bits indeterminate.
CS
0 1 2 3 4 5 6 7 8 9 10 11 12 13 1415 29 30 31 32 33 38 39 40 41 42 43 44 45 46 47
SCK
OP-CODE
24-bit Address
Mode bits
SI 0 0 0 0 1 0 1 1 X X X X X 18 17 16 _{2 1 0 7 6 1 0} Invalid
MSB
High-Z
LSB MSB LSB MSB Data Out LSB
SO
76543210
Invalid
FSTRD Command Sequence
CS
SCK
SI
SO
0 1 2 3 4 5 6 7 21 22 23 24 25 30 31 32 33 34 35 36 37 38 39
24-bit Address
X X X X X 18 17 16
MSB
High-Z
Mode bits
21076
1 0 Invalid
LSB MSB
LSB ^{MSB Data Out LSB}
76543210
Invalid
FSTRD Command Sequence (XIP mode)
DS501-00043-2v0-E
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