What Is ISP Pinout

ISP (In-System Programming) pinout is a direct hardware-level access method that allows technicians to communicate with the NAND storage of the Samsung SM-A35 (A356MEA) by connecting to dedicated test pads on the printed circuit board. Unlike software-based flashing that relies on a functioning bootloader or USB interface, ISP bypasses the normal boot chain entirely. This makes it possible to read, write, or erase data on the UFS memory chip directly through a compatible programmer. For the SM-A35, which runs on the Exynos 1380 platform with UFS 2.2 storage, ISP provides a reliable last-resort recovery path when conventional methods have failed. It is particularly valuable in professional repair environments where time and data integrity are critical.

When Technicians Use ISP

ISP access on the SM-A35 becomes necessary in a range of difficult repair scenarios, including:

  • Hard bootloop: Device continuously restarts and cannot enter recovery or download mode.
  • Dead boot (no power): Phone shows no signs of life after a failed OTA or manual flash attempt.
  • FRP (Factory Reset Protection) lock: Google account lock cannot be removed via software tools due to a corrupted or locked partition.
  • Locked or damaged bootloader: Normal EDL or Download Mode entry is blocked or non-functional.
  • Corrupt firmware partitions: Critical partitions such as BOOT, SYSTEM, or EFS are damaged and prevent normal operation.
  • IMEI/EFS recovery: Modem partition needs to be restored after data corruption.

SM-A35 ISP Test Points

The Samsung SM-A35 (A356MEA) uses a UFS interface to its NAND storage. The ISP test points are located on the rear side of the main PCB, typically near or beneath the UFS memory package. The key signal lines required for ISP access are listed below. Note that exact pad coordinates on the A356MEA PCB have not been independently verified in public documentation at the time of writing; technicians should cross-reference with a confirmed board-level diagram before probing.

  • CLK: UFS reference clock line
  • DATA0 (MOSI): Primary data input/output line
  • CMD: Command signal line
  • VCC: 2.9V–3.0V main power supply for UFS
  • VCCQ: 1.2V I/O voltage for UFS controller
  • GND: Ground reference point

How to Access the NAND

Follow these steps to perform ISP on the SM-A35:

  • Power off the device completely and remove the battery connector from the PCB.
  • Disassemble the device and expose the main motherboard, cleaning the ISP test pad area with isopropyl alcohol.
  • Identify the UFS test pads using a confirmed schematic or known ISP map for the A356MEA.
  • Solder thin-gauge ISP wires (30–32 AWG) carefully to each test point: CLK, DATA0, CMD, VCC, VCCQ, and GND.
  • Connect the wires to the ISP socket or pinout adapter on your programmer (e.g., EasyJTAG Plus or UMT).
  • Launch the programmer software, select Samsung SM-A35 or Exynos 1380 UFS profile, and power the board via the programmer's regulated supply.
  • Execute the desired operation: read, write, FRP erase, or partition restore.

Safety Tips and Precautions

Working at the ISP level carries significant risk if proper precautions are not followed:

  • ESD protection: Always wear an anti-static wrist strap and work on a grounded mat to prevent electrostatic discharge damage to the UFS controller.
  • Voltage regulation: Never exceed 3.0V on VCC or 1.2V on VCCQ. Overvoltage will permanently damage the UFS memory chip.
  • Soldering care: Use a fine-tip iron at no more than 300°C. Excessive heat can lift pads or damage nearby components.
  • Backup first: Always attempt a full read/backup of the UFS before performing any write or erase operation.
  • Verify pad identity: Confirm each test point with a multimeter before applying power to avoid short circuits.

Pin / Test Point Reference

PinDescription
CLKUFS reference clock signal line — Exact pad location on A356MEA PCB unconfirmed — verify with schematic
DATA0Primary UFS data input/output (MOSI) — Exact pad location on A356MEA PCB unconfirmed
CMDUFS command signal line — Exact pad location on A356MEA PCB unconfirmed
VCCMain power supply for UFS memory, 2.9V–3.0V — Do not exceed 3.0V
VCCQI/O voltage for UFS controller, 1.2V — Do not exceed 1.2V
GNDGround reference point — Multiple ground points available on PCB

Tools required: EasyJTAG Plus, UMT (Ultimate Multi Tool), Medusa Pro II, UFI Box, 30–32 AWG ISP wire, Fine-tip soldering iron (≤300°C), Anti-static wrist strap, Isopropyl alcohol (99%), Digital multimeter

Supported operations: FRP Erase, Dead Boot Repair, Read Firmware / Full UFS Backup, Write Firmware, IMEI / EFS Restore, Partition-Level Repair

⚠ Safety note: Use regulated voltage only: 2.9–3.0V VCC and 1.2V VCCQ. Overvoltage permanently destroys the UFS chip. Always ESD-protect the board. Verify pad identity with a multimeter before applying power.