STC15W204S-35I-SOP16 from STC Micro, in a SOIC-16. Pinout and pin descriptions extracted from the manufacturer datasheet by ds2sf; symbol, footprint, and 3D from KiCad-official CAD.

Pinout

Pin	Name	Type	Function
1	P1.2/T0/CMPO	bidirectional	Standard I/O P1[2]. Alt-functions: T0 (Timer/Counter 0 external input) and CMPO (on-chip comparator result output).
2	P1.3	bidirectional	Standard I/O P1[3]. No alternate function is exposed on this variant.
3	P1.4/T0CLKO	bidirectional	Standard I/O P1[4]. Alt-function: T0CLKO - Timer/Counter 0 clock output (enable via INT_CLKO[0]); can also output a divided version of the T0 external clock input.
4	P1.5	bidirectional	Standard I/O P1[5]. No alternate function is exposed on this variant.
5	P5.4/RST/MCLKO/CMP-	bidirectional	Standard I/O P5[4]. Alt-functions: RST (active-HIGH reset input), MCLKO (main-clock output at MCLK/1, /2 or /4 - internal R/C clock only on this series), CMP- (comparator negative input; requires high-impedance input mode when used as comparator).
6	VCC	power_in	Positive supply, 2.5 V to 5.5 V.
7	P5.5/CMP+	bidirectional	Standard I/O P5[5]. Alt-function: CMP+ - comparator positive input (requires high-impedance input mode when used as comparator).
8	GND	power_in	Ground / supply negative reference.
9	P3.0/RxD/INT4/T2CLKO	bidirectional	Standard I/O P3[0]. Alt-functions: RxD (UART receive), INT4 (falling-edge external interrupt 4, supports power-down wake-up), T2CLKO (Timer 2 clock output, enabled via INT_CLKO[2]).
10	P3.1/TxD/T2	bidirectional	Standard I/O P3[1]. Alt-functions: TxD (UART transmit), T2 (Timer/Counter 2 external input).
11	P3.2/INT0	bidirectional	Standard I/O P3[2]. Alt-function: INT0 - external interrupt 0; edge sensitivity selected by IT0 (TCON.0): rising+falling when 0, falling-only when 1. Supports power-down wake-up.
12	P3.3/INT1	bidirectional	Standard I/O P3[3]. Alt-function: INT1 - external interrupt 1; edge sensitivity selected by IT1 (TCON.2): rising+falling when 0, falling-only when 1. Supports power-down wake-up.
13	P3.6/INT2/RxD_2	bidirectional	Standard I/O P3[6]. Alt-functions: INT2 (falling-edge external interrupt 2, supports power-down wake-up), RxD_2 (alternate UART receive - the UART can be time-multiplexed between P3.0/P3.1 and P3.6/P3.7 pin groups).
14	P3.7/INT3/TxD_2	bidirectional	Standard I/O P3[7]. Alt-functions: INT3 (falling-edge external interrupt 3, supports power-down wake-up), TxD_2 (alternate UART transmit - see P3.6 note).
15	P1.0/RSTOUT_LOW	bidirectional	Standard I/O P1[0]. Alt-function: RSTOUT_LOW - outputs low after power-on and during reset; the user may drive it high or low in software. If used as an input, drive high first before reading.
16	P1.1	bidirectional	Standard I/O P1[1]. No alternate function is exposed on this variant.

Key specifications

Parameter	Value
Manufacturer	STC Micro
Package	SOIC-16
Category	MCU
Pins	16

Ordering variants

Same part, different packaging or reel option.

STC15W204S-35I-SOP16
STC15W204S-35I-DIP16
STC15W204S-35I-SOP8

CAD (KiCad official)

Symbol: STC15W204S-35I-SOP16
Footprint: Package_SO:SOIC-16_3.9x9.9mm_P1.27mm
3D model: SOIC-16 (KiCad packages3D, STEP)

Provenance

Data extracted from the manufacturer datasheet, not a distributor listing:

Datasheet: STC Micro datasheet (1219 pp, sha256 cc8c299c891646e0, retrieved 2026-08-17, tier: lcsc)
Datasheet language: Chinese. Pin names, descriptions, and specs on this page were extracted and translated to English by ds2sf; the linked PDF is the manufacturer original.
Extractor: ds2sf (Claude). Every pin and dimension is cited to a datasheet page; it refuses to fabricate.
CAD: KiCad official libraries (CC-BY-SA 4.0).

Datasheet PDF