STC89C52RC-40I-LQFP44 from STC Micro, in a LQFP-44(10x10). 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	P1.5	bidirectional	Standard quasi-bidirectional I/O port PORT1[5]. Internal weak pull-up; drives/reads CMOS level.
2	P1.6	bidirectional	Standard quasi-bidirectional I/O port PORT1[6]. Optionally connects to external crystal for the on-chip USB-serial helper circuit in some board layouts.
3	P1.7	bidirectional	Standard quasi-bidirectional I/O port PORT1[7].
4	RST	input	Active-high reset input. HD-version parts have an internal 45k-100k pull-down to GND; hold high for at least two machine cycles to reset the MCU.
5	P3.0/RxD	bidirectional	P3.0 general-purpose I/O; alternate function RxD = UART1 serial data receive input.
6	P4.3/INT2	bidirectional	P4.3 general-purpose I/O; alternate function INT2 = external interrupt 2 (falling-edge or low-level trigger).
7	P3.1/TxD	bidirectional	P3.1 general-purpose I/O; alternate function TxD = UART1 serial data transmit output.
8	P3.2/INT0	bidirectional	P3.2 general-purpose I/O; alternate function INT0 = external interrupt 0 (falling-edge or low-level trigger).
9	P3.3/INT1	bidirectional	P3.3 general-purpose I/O; alternate function INT1 = external interrupt 1 (falling-edge or low-level trigger).
10	P3.4/T0	bidirectional	P3.4 general-purpose I/O; alternate function T0 = Timer/Counter 0 external clock/count input.
11	P3.5/T1	bidirectional	P3.5 general-purpose I/O; alternate function T1 = Timer/Counter 1 external clock/count input.
12	P3.6/WR	bidirectional	P3.6 general-purpose I/O; alternate function WR = active-low external data memory write strobe (for MOVX instructions).
13	P3.7/RD	bidirectional	P3.7 general-purpose I/O; alternate function RD = active-low external data memory read strobe (for MOVX instructions).
14	XTAL2	output	Output of the internal inverting oscillator amplifier; connect to the second lead of the external crystal. If an external clock source is used on XTAL1, XTAL2 outputs the buffered clock and may be left floating.
15	XTAL1	input	Input to the internal inverting oscillator amplifier; connect to one lead of the external crystal or directly to an external clock source.
16	GND	power_in	Digital ground (0 V reference).
17	P4.0	bidirectional	Standard quasi-bidirectional I/O port PORT4[0]. Present only on LQFP-44/PLCC-44 packages (not on PDIP-40).
18	P2.0	bidirectional	P2 quasi-bidirectional I/O with internal pull-ups. Doubles as high address byte A8 when accessing external memory via MOVX @DPTR / MOVC.
19	P2.1	bidirectional	P2 quasi-bidirectional I/O; doubles as external address bit A9.
20	P2.2	bidirectional	P2 quasi-bidirectional I/O; doubles as external address bit A10.
21	P2.3	bidirectional	P2 quasi-bidirectional I/O; doubles as external address bit A11.
22	P2.4	bidirectional	P2 quasi-bidirectional I/O; doubles as external address bit A12.
23	P2.5	bidirectional	P2 quasi-bidirectional I/O; doubles as external address bit A13.
24	P2.6	bidirectional	P2 quasi-bidirectional I/O; doubles as external address bit A14.
25	P2.7	bidirectional	P2 quasi-bidirectional I/O; doubles as external address bit A15.
26	P4.4/PSEN	bidirectional	P4.4 general-purpose I/O; alternate function PSEN = Program Store Enable, active-low strobe for external program memory reads.
27	P4.5/ALE	bidirectional	P4.5 general-purpose I/O; alternate function ALE = Address Latch Enable output for demultiplexing the low address byte on P0 during external memory access. Also acts as PROG programming pulse input during Flash ISP.
28	P4.1	bidirectional	Standard quasi-bidirectional I/O port PORT4[1]. Present only on LQFP-44/PLCC-44 packages.
29	P4.6/EA	bidirectional	P4.6 general-purpose I/O; alternate function EA = External Access Enable. Internally pulled up to VCC: floating or tied high starts execution from internal Flash; tied to GND starts execution from external program memory.
30	P0.7/AD7	bidirectional	P0.7 8-bit quasi-bidirectional I/O (open-drain after reset; requires 4.7k-10k external pull-up when used as GPIO). Doubles as multiplexed low address/data line AD7 during external memory access (no external pull-up needed in bus mode).
31	P0.6/AD6	bidirectional	P0.6 open-drain quasi-bidirectional I/O; doubles as multiplexed address/data line AD6.
32	P0.5/AD5	bidirectional	P0.5 open-drain quasi-bidirectional I/O; doubles as multiplexed address/data line AD5.
33	P0.4/AD4	bidirectional	P0.4 open-drain quasi-bidirectional I/O; doubles as multiplexed address/data line AD4.
34	P0.3/AD3	bidirectional	P0.3 open-drain quasi-bidirectional I/O; doubles as multiplexed address/data line AD3.
35	P0.2/AD2	bidirectional	P0.2 open-drain quasi-bidirectional I/O; doubles as multiplexed address/data line AD2.
36	P0.1/AD1	bidirectional	P0.1 open-drain quasi-bidirectional I/O; doubles as multiplexed address/data line AD1.
37	P0.0/AD0	bidirectional	P0.0 open-drain quasi-bidirectional I/O; doubles as multiplexed address/data line AD0.
38	VCC	power_in	Positive supply. 5V for STC89C52RC (operating range typically 3.8-5.5 V); 3.3V for STC89LE52RC (2.0-3.6 V). Decouple with 100 nF + 10 uF close to the pin.
39	P4.2/INT3	bidirectional	P4.2 general-purpose I/O; alternate function INT3 = external interrupt 3 (falling-edge or low-level trigger).
40	P1.0/T2	bidirectional	P1.0 general-purpose I/O; alternate function T2 = Timer/Counter 2 external clock/count input.
41	P1.1/T2EX	bidirectional	P1.1 general-purpose I/O; alternate function T2EX = Timer 2 capture/reload trigger control input.
42	P1.2	bidirectional	Standard quasi-bidirectional I/O port PORT1[2].
43	P1.3	bidirectional	Standard quasi-bidirectional I/O port PORT1[3].
44	P1.4	bidirectional	Standard quasi-bidirectional I/O port PORT1[4].

Key specifications

Parameter	Value
Manufacturer	STC Micro
Package	LQFP-44(10x10)
Category	MCU
Pins	44

Ordering variants

Same part, different packaging or reel option.

STC89C52RC-40I-LQFP44
STC89LE52RC-40I-LQFP44
STC89C52RC-40I-PDIP40
STC89C52RC-40C-PDIP40
STC89C52RC-40I-PLCC44

CAD (KiCad official)

Symbol: STC89C52RC-40I-LQFP44
Footprint: Package_QFP:LQFP-44_10x10mm_P0.8mm
3D model: LQFP-44(10x10) (KiCad packages3D, STEP)

3D model downloads

Two STEP files. Same geometry, different body top:

File	Size	Use it when
`stc89c52rc-40i-lqfp44.step`	591 KB	You want the bare part, or you mark your own boards.
`stc89c52rc-40i-lqfp44-etched.step`	5.6 MB	You want the part with `STC89C52RC-40I-LQFP44` already on it.

The marking in the etched file is real recessed geometry cut into the solid, not a texture or a decal: 1387 faces against 695 in the bare model. It survives export, section views, and rendering in any CAD tool, and it drops straight into KiCad or Fusion with no extra setup.

Provenance

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

Datasheet: STC Micro datasheet (1691 pp, sha256 fac7be430b93e2dd, 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