1. Device Overview: ️· Type: SPI Flash Memory
️· Models: GD25D40C and GD25D20C (slight differences in ID definitions - see below)
️· Purpose: Designed for data storage in embedded systems.
2. Core Concepts & Registers ️· Write Enable Latch (WEL): Must be set to 1 before programming/erasing. Set by WREN (06H), cleared by WRDI (04H) and automatically reset after WRSR.
️· Status Register: Contains information about the device's status, including the Write In Progress (WIP) bit. Read by RDSR (05H), some bits modified by WRSR (01H).
️· Write In Progress (WIP): Indicates whether a programming or erasing operation is in progress.
️· Block Protect (BP2, BP1, BP0): These bits determine the size of the read-only area (specifics not fully described but configurable via WRSR).
️· Status Register Protect (SRP): Used in conjunction with the Write Protect (WP#) signal to control access (Hardware Protection Mode).
️· Hardware Protection Mode (HPM): A mode that restricts write operations, enabled by SRP and WP#.
3. Command Summary (Hex Codes and Functionality):
| Command (Hex) |
Functionality |
Notes |
| 06H (WREN) |
Write Enable: Sets the WEL latch to 1. |
Required before programming or erasing. |
| 04H (WRDI) |
Write Disable: Resets the WEL latch to 1. |
|
| 05H (RDSR) |
Read Status Register: Reads the Status Register. |
|
| 01H (WRSR) |
Write Status Register: Modifies the Status Register. |
Requires WEL to be set. Affects BP bits and SRP. Not executable in HPM. |
| 03H (READ) |
Read Data Bytes: Reads data from memory. |
Incrementing address after each byte read. |
| 0BH (READS) |
Read Data Bytes at Higher Speed: Reads data rapidly. |
Uses a dummy byte. Incrementing address after each byte read. |
| ABH |
Release From Deep Power-Down & Read Device ID |
|
| 90H |
Manufacturer/Device ID |
| 9FH |
Read Identification |
| 4BH |
Read Unique ID |
4. ID Definitions (Differences between GD25D40C and GD25D20C):
| Operation Code |
M7-M0 (GD25D40C) |
ID15-ID8 (GD25D40C) |
ID7-ID0 (GD25D40C) |
M7-M0 (GD25D20C) |
ID15-ID8 (GD25D20C) |
ID7-ID0 (GD25D20C) |
| 9FH |
C8 |
40 |
13 |
C8 |
40 |
12 |
| 90H |
C8 |
|
12 |
C8 |
|
11 |
| ABH |
|
|
12 |
|
|
11 |
Key Takeaways: ️· SPI Interface: This is an SPI device, so it uses chip select (CS#), data input (DI), data output (DO), and clock (SCK) signals.
️· Timing: The document refers to specific timing parameters (fR, fC, tW) that would be important for hardware implementation.
️· Protection: Offers various protection mechanisms to prevent unauthorized writes.
️· ID Codes: Device identification codes (MID, DID) are provided to allow software to identify the specific flash memory chip.