What Is ISP Pinout

ISP (In-System Programming) pinout is a hardware-level technique that allows technicians to access a device's NAND flash memory — either eMMC or UFS — directly through exposed test pads on the printed circuit board. Rather than relying on the device's operating system or bootloader, ISP bypasses software entirely by connecting compatible read/write hardware straight to the storage chip's interface lines. This method is essential when conventional software tools fail, as it grants raw access to partition data, bootloaders, and user storage regions at the chip level.

When Technicians Use ISP

ISP is not a first-resort tool — it is used when standard recovery and fastboot methods are no longer viable. Common scenarios include:

  • Hard bootloop: The device restarts endlessly and cannot enter recovery or download mode.
  • Dead device (no power): The phone does not respond to charging or power buttons, yet the board is electrically intact.
  • Failed OTA or flash: An interrupted firmware update has left the storage in a corrupt or unbootable state.
  • FRP (Factory Reset Protection) lock: The Google account lock cannot be cleared through software tools, requiring direct partition editing.
  • IMEI or EFS restoration: The EFS partition needs to be restored after data loss.

SM-A156 ISP Test Points

The Samsung SM-A156 5G uses a MediaTek Dimensity 6100+ platform. The primary storage interface is routed to test pads located near the main storage IC on the rear side of the main PCB. The standard eMMC/UFS ISP signals to locate are CLK, CMD, DAT0, VCC, VCCQ, and GND. Because Samsung frequently revises PCB layouts between production batches, pad coordinates should be verified against the physical board using a multimeter in continuity mode before connecting any ISP tool.

  • CLK: Clock signal line — drives data transfer timing.
  • CMD: Command line — carries read/write instructions to the storage chip.
  • DAT0: Primary data line used in single-bit ISP mode.
  • VCC: Main storage supply voltage (typically 3.3 V for eMMC; confirm on board).
  • VCCQ: I/O supply voltage (typically 1.8 V).
  • GND: Common ground reference.

Reading and Writing Procedure

Before beginning, ensure all required drivers and box software are fully updated.

  • Fully power down the device and disconnect the battery.
  • Disassemble the handset and expose the main PCB.
  • Identify the ISP test pads using a verified pinout diagram and multimeter confirmation.
  • Solder thin ISP wires or use a compatible ISP pogo-pin jig to each pad.
  • Connect to your ISP box or adapter and launch the corresponding software.
  • Select the correct platform (MediaTek / MT6835) and storage type.
  • Initiate a full read (backup) before any write or erase operation.
  • Perform the desired operation: firmware write, FRP erase, or partition restore.
  • Safely disconnect, reassemble, and test the device.

Safety Tips Before You Start

  • ESD protection: Always wear an anti-static wrist strap and work on a grounded mat.
  • Power off completely: Remove the battery before soldering to any test pad.
  • Voltage verification: Confirm VCC and VCCQ levels with a multimeter before supplying power through the ISP tool.
  • Full backup first: Read and save a complete dump before writing or erasing any data.
  • Use correct box settings: Applying wrong voltage or incorrect chip parameters can permanently damage the storage IC.
  • Inspect solder joints: Cold or bridged joints on CLK or CMD pads will cause read failures or corrupt writes.

Pin / Test Point Reference

PinDescription
CLKClock signal for eMMC/UFS interface — Exact pad location unconfirmed; verify with multimeter
CMDCommand line for storage chip communication — Exact pad location unconfirmed; verify with multimeter
DAT0Primary data line used in ISP single-bit mode — Exact pad location unconfirmed; verify with multimeter
VCCMain storage supply voltage (typically 3.3 V) — Confirm voltage on board before applying power
VCCQI/O voltage rail for storage chip (typically 1.8 V) — Confirm voltage on board before applying power
GNDCommon ground reference point on PCB

Tools required: EasyJTAG Plus, UMT (Ultimate Multi Tool), Medusa PRO II, UFi Box, ISP pogo-pin jig or fine ISP wires, Multimeter (for pad continuity verification)

Supported operations: Read Firmware (Full Dump), Write Firmware, FRP Erase, Dead Boot Repair, EFS / IMEI Restore, Partition Backup and Restore

⚠ Safety note: Always disconnect battery before connecting ISP wires. Verify VCC (3.3 V) and VCCQ (1.8 V) before powering. Incorrect voltage or wrong chip selection may permanently destroy the storage IC. Back up a full dump before any write or erase operation.