| Pin Number |
Description |
| 1-8 |
P1.0 - P1.7 - Port 1 |
| 9 |
RST - Reset |
| 10 |
P3.0/RXD - Port 3.0 / Serial Receive Pin |
| 11 |
P3.1/TXD - Port 3.1 / Serial Transmit Pin |
| 12 |
P3.2/INT0 - Port 3.2 / Interrupt 0 (Active Low) |
| 13 |
P3.3/INT1 - Port 3.3 / Interrupt 1 (Active Low) |
| 14 |
P3.4/T0 - Port 3.4 / Timer 0 |
| 15 |
P3.5/T1 - Port 3.5 / Timer 1 |
| 16 |
P3.6/WR - Port 3.6 / Write (Active Low) |
| 17 |
P3.7/RD - Port 3.7 / Read (Active Low) |
| 18 |
XTAL2 - Crystal Input |
| 19 |
XTAL1 - Crystal Input |
| 20 |
Vss - Ground |
| 21 - 28 |
P2.0 - P2.7 - Port 2 |
| 29 |
PSEN - Program Store Enable (Active Low) |
| 30 |
ALE - Address Latch Enable |
| 31 |
EA - External Memory Enable (Active Low) |
| 32 - 39 |
P0.7 - P0.1 - Port 0 |
| 40 |
Vcc - Positive Supply |