An ISO/IEC 7816 contact smart card is an ID-1 card with an embedded chip, accessed through a gold pad of eight contacts (C1–C8). ISO/IEC 7816-2 fixes the contact positions and ISO/IEC 7816-3 defines the electrical interface and transmission protocols. The card has no clock of its own — it is powered and clocked by the reader — and exchanges data over a single half-duplex bidirectional I/O line. These cards are the basis of SIM/UICC and EMV bank cards.
8 Pin Connector at the card.
| Pin | Name | Description |
|---|---|---|
| 1 | VCC | Supply voltage (5 V class A, 3 V class B, 1.8 V class C) |
| 2 | RST | Reset signal |
| 3 | CLK | Clock signal |
| 4 | RFU | Reserved (USB D+ on USB-capable cards) |
| 5 | GND | Ground |
| 6 | VPP / SPU | Programming voltage (legacy, deprecated; SWP on modern UICCs) |
| 7 | I/O | Serial data input/output (half-duplex) |
| 8 | RFU | Reserved (USB D− on USB-capable cards) |
Notes
- Supply classes. The card’s supply voltage (C1, VCC) is one of three classes: 5 V (class A), 3 V (class B) or 1.8 V (class C); the card declares which it supports in its Answer-to-Reset.
- External clock and reset. The reader supplies the clock on C3 and resets the card on C2; after reset the card returns an Answer-to-Reset (ATR). The card does not generate its own clock.
- Single I/O line. All data travels on C7 (I/O) in half-duplex — the reader and card never transmit at the same time, using the T=0 or T=1 protocol.
- VPP deprecated. C6 originally supplied a programming voltage (VPP, historically up to ~21 V); since cards now generate it internally this use is deprecated, and ISO 7816-3 renames the contact SPU. On modern SIM/UICC cards C6 carries the Single Wire Protocol (SWP) to the NFC front-end.
- Reserved contacts. C4 and C8 are reserved; on USB-capable cards they carry USB D+ and D−.
Signals
- VCC (C1) — supply voltage (5 V, 3 V or 1.8 V).
- RST (C2) — reset input; triggers the Answer-to-Reset.
- CLK (C3) — external clock supplied by the reader.
- GND (C5) — ground / reference voltage.
- VPP / SPU (C6) — legacy programming voltage (deprecated); SWP on modern UICCs.
- I/O (C7) — single half-duplex bidirectional serial data line.
- RFU (C4, C8) — reserved; USB D+ and D− on USB-capable cards.
References
- ISO/IEC 7816-2:1999 — dimensions and location of the contacts (ISO preview) — the authoritative C1–C8 contact assignment.
- ISO/IEC 7816-3:2006 — electrical interface and transmission protocols — the VCC classes, half-duplex I/O, external clock and the VPP/SPU deprecation.