ISD94100 Series Technical Reference Manual
Sep 9, 2019
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multi-word write operation needs to write at least 16 bytes (4 words), and can write up to 512 bytes.
No matter how many bytes are to be written in one multi-word write session, there is only one flash
SETUP time before writing and only one HOLD time after writing, as shown in Figure 6.4-11 below.
32-bit
Programming
64-bit
Programming
Multi-Word
Programming
SETUP
TIME
fix 4 bytes programming
HOLD
TIME
SETUP
TIME
fix 8 bytes programming
HOLD
TIME
SETUP
TIME
16 ~ 512 bytes programming (16 bytes align)
HOLD
TIME
Time
Figure 6.4-11 Timeline comparison for write operations
Within a multi-word programming session, the firmware needs to monitor buffer status, continuously
prepare next batch two bytes of data in time to ensure a successful programming session. Because
fetching code from APROM or LDROM cannot keep up with this pace, multi-word programing
firmware code should run from SRAM.
Cortex-M4 CPU
Flash
Operation Control
Embedded Flash Memory
(APROM)
(LDROM)
(Data Flash)
Flash
Control
Registers
AHB Slave Interface
Flash Memory Controller
Embedded SRAM
Figure 6.4-12 Firmware in SRAM for Multi-word Programming