It may be used for external timing or clocking purposes.In normal operation ALE is emitted at a constant rate of 1/6 the oscillator frequency.Address Latch Enable output pulse for latching the low byte of the address during accesses to external memory.This pin left unconnected when internal code memory is using for program memory.PSEN is the read strobe to external program memory.The output pin 29 is designated for PSEN.In this case port-0 and port-2 can not be used for general purpose I/Os. The chip has capability to interface with memory of 8-bit data bus and maximum of 16-bit address bus. The Port-3 output buffers can sink/source four TTL inputsĪn external memory of maximum 64KB can be attached with AT89C52.Port-3 is an 8-bit bi-directional I/O port with internal pull ups.The pins are designated as P3.0 to P3.7.Port-3 is a dedicated port on pins 10-17.Port-2 emits the high-order address byte during fetches from external program memory.The port-2 output buffers can sink/source four TTL inputs.Port-2 is an 8-bit bi-directional I/O port with internal pull-ups.The pins are designated as P2.0 to P2.7 (A8-A15).
Port-2 is a dual-purpose port dedicated on pins 21-28.The port-1 output buffers can sink/source four TTL inputs.Port-1 is an 8-bit bi-directional I/O port with internal pull ups.P1.1/T2 EX can also be configured as timer/counter-2 external trigger input.P1.0/T2 can also be configured as timer/counter-2 input.The pins are designated as P1.0 (T2), P1.1 (T2 EX) to P1.7.Port-1 is a dedicated I/O port on pins 1-8.External pull-ups are required when this port is used for general purpose output port.Port-0 may also be configured to be the multiplexed low-order address/data bus during accesses to external program and data memory.Port-0 is an 8-bit open-drain bi-directional I/O port.The pins are designated as P0.0 to P0.7 (AD0-AD7).Port-0 is a dual-purpose port dedicated on pins 32-39.
The 32 I/Os are divided into 4 ports and each port has 8 I/Os. The chip has 32 I/Os for external world interfacing.
0 kommentar(er)
