Spark Logic

Atmel AT89C52 connection guide

Atmel AT89C52 PQFP-44 wiring guide with power, signal assignments, and bench checks.

PDIP-40 40 contacts
PLCC-44 44 contacts
TQFP-44 44 contacts

PQFP-44

44 contacts Current package

Atmel · 44Q, 0.80 mm lead pitch, 12.95–13.45 mm lead span and 2.45 mm maximum height. Ordering suffix Q.

Up to 16 MHz, 4.0–6.0 V. AT89C52-16QC: 0–70 °C. AT89C52-16QI: −40–85 °C. 8 KiB Flash and 256 B RAM.

Power and internal code selection

Required

Power VCC from a regulated 5 V supply (±5% for these examples). Place a 100 nF ceramic bypass between VCC and GND. The high strap on EA selects the installed Flash at reset address 0000h.

100 nF between VCC rail and GroundVCC rail100 nFGround

Bench checks

  • Confirm the package pin 1 mark before applying power and measure VCC relative to ground at the IC.
  • Use a 100 nF X7R capacitor rated at least 16 V as the local high-frequency bypass. Keep its loop short.
  • Confirm the on-chip Flash contains the intended startup code before selecting internal execution.

Atmel AT89C52, 0313H–02/00, pp. 4, 17, 22

Connection scenarios

Connect a logic-level UART

Wire RXD and TXD to the opposite UART signals, with a shared ground. Use the logic-level side of a compatible adapter. A conventional RS-232 port requires a transceiver.

Bench checks

  • At 5 V ±5%, verify adapter TXD HIGH ≥ 1.95 V and LOW ≤ 0.85 V. Adapter RXD must accept the 2.4 V guaranteed MCU HIGH at no more than 60 µA source load.
  • Set P3.0 and P3.1 latches to 1, use serial mode 1 and match the baud rate, framing and parity at both ends.
  • At 11.0592 MHz, Timer 1 mode 2 with TH1 = TL1 = FDh and SMOD = 0 gives 9600 baud nominal. The calculation is 11.0592 MHz ÷ (12 × 32 × 3).

Atmel AT89C52, 0313H–02/00, pp. 3, 11, 17, and Intel MCS-51 User’s Manual, serial interface

PQFP-44 wiring map

Highlighted contacts are used in the required step or selected circuit. Select a contact to inspect it.

PQFP-44
Top view, index corner at upper left. Pin 1 is the topmost lead on the left edge. Scroll the map to reach all contacts.
Selected pin details

5 · P3.0

Bidirectional · Bidirectional

Quasi-bidirectional I/O with internal pull-up. A latch value of 1 releases the pin for input. RXD receives UART data in asynchronous modes and carries serial data in shift-register mode. Keep the corresponding latch bit at 1 for the alternate function.

After reset · Latch = 1. Pulled HIGH when the pin is unloaded and used as GPIO.

Atmel 0313H–02/00, pp. 1, 3–5

Electrical limits · Pin in the reference

Models and documents

This reference resolves the abbreviated 89C52 name to Atmel’s AT89C52, document 0313H. It covers all four package drawings and the listed 12/16/20/24 MHz speed grades. Check the full marking on parts from other manufacturers. The AT89S52 uses its own programming interface and datasheet.

AT89C52-12
Up to 12 MHz, 4.0–6.0 V. AT89C52-12QC: 0–70 °C. AT89C52-12QI: −40–85 °C. 8 KiB Flash and 256 B RAM.
AT89C52-16
Up to 16 MHz, 4.0–6.0 V. AT89C52-16QC: 0–70 °C. AT89C52-16QI: −40–85 °C. 8 KiB Flash and 256 B RAM.
AT89C52-20
Up to 20 MHz, 4.0–6.0 V. AT89C52-20QC: 0–70 °C. AT89C52-20QI: −40–85 °C. 8 KiB Flash and 256 B RAM.
AT89C52-24
Up to 24 MHz, 4.0–6.0 V. AT89C52-24QC: 0–70 °C. AT89C52-24QI: −40–85 °C. 8 KiB Flash and 256 B RAM.
  • Datasheet for AT89C52· Atmel 0313H–02/00, February 2000. Pin configurations p. 1, pin descriptions pp. 3–4, SFR reset p. 5, Timer 2 pp. 6–10, oscillator p. 12, DC p. 17, clock drive p. 20, ordering and package drawings pp. 22–23. SHA-256 f8d392b5cc25322766180e74d323b5c8abd647c98f9d4fbfc6f99a7d1f89e4bd.
  • Intel MCS-51 Family User’s Manual· Intel 272383-002, February 1994, chapter 3. Core operation, port latches and serial interface. The AT89C52 datasheet governs its own electrical limits and Timer 2 extensions.