The **SD-R** (Secure Digital - Recordable) card is a specialized version of the standard SD card architecture designed primarily for "Write Once, Read Many" (WORM) applications or secure content distribution. Below is an explanation of its electronic components and architectural layers. --- ### 1. Internal Block Diagram The internal structure of an SD-R card consists of three main electronic segments: | Component | Function | | :--- | :--- | | **Flash Memory Die** | The physical storage area (usually NAND Flash). | | **SD Controller** | The "brain" that manages communication, error correction, and wear leveling. | | **Interface Logic** | The physical pins and registers used to talk to the host device (SPI or SD mode). | --- ### 2. Key Electronic Components #### A. NAND Flash Memory Unlike standard SD cards that use rewritable Multi-Level Cell (MLC) or Triple-Level Cell (TLC) flash, SD-R cards often utilize: * **WORM Logic:** Integrated at the firmware or hardware level to prevent the memory cells from being erased or overwritten once a bit is set. * **OTP (One-Time Programmable) Areas:** Specific sectors where data is "burned" permanently. #### B. The Controller (ASIC/MCU) The controller is an Integrated Circuit (IC) that handles the complex signaling: * **Error Correction Code (ECC):** Since SD-R cards are used for long-term archiving, the ECC ensures data integrity against "bit rot." * **Security Protocol Engine:** Manages CPRM (Content Protection for Recordable Media). * **Write-Protection Logic:** The controller ignores any `CMD24` (Write Block) commands directed at sectors that have already been written. #### C. Passive Components On the PCB (Printed Circuit Board) inside the plastic casing, you will find: * **Decoupling Capacitors:** Small SMD components that stabilize the voltage (usually 2.7V to 3.6V) to prevent data corruption during power fluctuations. * **Resistors:** Used for impedance matching on high-speed data lines. --- ### 3. Pinout Configuration The SD-R follows the standard 9-pin SD interface: | Pin # | Name | Type | Description | | :--- | :--- | :--- | :--- | | 1 | CD/DAT3 | I/O/PP | Card Detect / Data Line 3 | | 2 | CMD | PP | Command/Response | | 3 | VSS1 | S | Ground | | 4 | VDD | S | Supply Voltage | | 5 | CLK | I | Clock | | 6 | VSS2 | S | Ground | | 7 | DAT0 | I/O/PP | Data Line 0 | | 8 | DAT1 | I/O/PP | Data Line 1 | | 9 | DAT2 | I/O/PP | Data Line 2 | --- ### 4. Specialized SD-R Features 1. **Permanent Write Protect:** While standard SD cards have a mechanical switch, SD-R cards have an electronic "flag" in the **CSD (Card Specific Data)** register that identifies the card as non-erasable. 2. **Authentication:** Many SD-R parts include a unique **ID (CID Register)** that is cryptographically linked to the stored content to prevent cloning. ---