ISP (In-System Programming)
Definition
A variant of direct chip access that connects to the eMMC command and data pins while the chip is still on the board, bypassing the processor. ISP sits between JTAG and chip-off in terms of invasiveness and is sometimes used when TAP contacts are unavailable but the eMMC pads are accessible.
- Target
- eMMC command and data pins
- Bypasses
- Device processor
- Invasiveness
- Between JTAG and chip-off
- Used when
- TAP contacts unavailable, eMMC pads accessible
Common questions
Why choose ISP over JTAG for a given device?+
JTAG requires access to the device's test access port pins, which are not present or documented on every board. If those pads are missing but the eMMC chip's own pins are reachable while still soldered down, ISP lets the examiner read the chip directly without the destructive step of desoldering it.
How does ISP avoid the risks of full chip-off extraction?+
Because the eMMC chip stays mounted on the board during acquisition, ISP avoids the heat damage and irreversibility risk of desoldering the chip, though it still requires precise physical access to solder or probe the correct pads and is more technically demanding than a standard cable-based logical extraction.
Related terms
- Chip-Off Acquisition
- A physical extraction method in which the flash memory chip is desoldered from the device's circuit board and read directly with specialised...
- eMMC (Embedded MultiMediaCard)
- A flash storage standard that packages NAND memory chips and a controller into one soldered module using a parallel interface. Common in...
- JTAG (Joint Test Action Group)
- The industry group that produced IEEE standard 1149.1, which defines the test access port and boundary-scan architecture built into most modern integrated...
- Pinout
- A diagram or database entry that maps each physical contact on a device's circuit board to its signal function. For JTAG acquisition,...
- Test Access Port (TAP)
- The set of four or five contact pads (TDI, TDO, TCK, TMS, and optionally TRST) on a circuit board that implement the...