| Сигнал | AT89C1051 | AT89C2051 | AT89C4051 | AT89C51 |
| RDY/BSY | 3 (P3.1) | 14 (P3.4) | ||
| PROG | 6 (P3.2) | 30 (ALE) | ||
| Dat1 | 7 (P3.3) | 27 (P2.6) | ||
| Dat2 | 8 (P3.4) | 28 (P2.7) | ||
| Dat3 | 9 (P3.5) | 16 (P3.6) | ||
| Dat4 | 11 (P3.7) | 17 (P3.7) | ||
| IncrAddr | 5 (XTAL1) | - 19? - | ||
| Data | 12...19 (P1) | 39...32 (P0) | ||
| Vcc | 20 | 40 | ||
| GND | 10 | 20 | ||
| RST | 1 | 9 | ||