Microcontroller not blinking LED

Question

I want to check if my microcontroller is working. It's the first time I'm working with microcontrollers. I followed this tutorial to blink a LED at the P1.0 pin, but nothing is happening.

My microcontroller is AT89S51. My operating system is macOS Ventura. I'm using Arduino Leonardo as an ISP programmer. Using BC548 transistor.

My Assembly code:

; Blink an LED connected to Pin P1.0 every second
 ORG 0H
 ; set P1.0 as output
 MOV P1, #00000001B
LOOP: ; turn on LED
 SETB P1.0
 ; delay for 500ms
 ACALL DELAY
 ; turn off LED
 CLR P1.0
 ; delay for 500ms
 ACALL DELAY
 ; jump back to the beginning of the loop
 JMP LOOP
DELAY: ; delay for 500ms
 MOV R1, #10
 MOV R2, #200
DELAY_LOOP:
 DJNZ R1, $
 DJNZ R2, DELAY_LOOP
 RET
 END

Creating .hex file:

@~ : c51asm blink.asm
C51ASM: advanced C51 macro assembler Version 1.2 (06 May 2011)
Copyright (C) 2011 Atmel Corp.
Pass 1 completed with no warnings and no errors
Pass 2 completed with no warnings and no errors
Segment usage:
 Code : 22 bytes
 Data : 0 bytes
 Idata : 0 bytes
 Edata : 0 bytes
 Fdata : 0 bytes
 Xdata : 0 bytes
 Bit : 0 bits
 Register banks used: ---
 Warnings: 0
 Errors: 0

Writing into the microcontroller flash memory, where the file F40R96CIUSLFZFP.conf is defined here:

@~ : avrdude -C ~/micro/F40R96CIUSLFZFP.conf -c stk500v1 -P /dev/cu.usbmodem1101 -p 89s51 -b 19200 -U flash:w:/Users/me/blink.hex

Output:

avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.01s
avrdude: Device signature = 0x1e5106 (probably 89s51)
avrdude: NOTE: "flash" memory has been specified, an erase cycle will be performed
 To disable this feature, specify the -D option.
avrdude: erasing chip
avrdude: reading input file "/Users/me/blink.hex"
avrdude: input file /Users/me/blink.hex auto detected as Intel Hex
avrdude: writing flash (68 bytes):
Writing | ################################################## | 100% 0.14s
avrdude: 68 bytes of flash written
avrdude: verifying flash memory against /Users/me/blink.hex:
avrdude: input file /Users/me/blink.hex auto detected as Intel Hex
Reading | ################################################## | 100% 0.05s
avrdude: 68 bytes of flash verified
avrdude done. Thank you.

Everything seems to be fine, but nothing happens (LED is not blinking). I don't know if I'm supposed to connect or disconnect something after the upload, but I guess it should start blinking right away(?). My connection images are below (although I've triple-checked).

enter image description here enter image description here

• Justme: It's impossible to see how the LED is connected and where, to see if there are any mistakes.
• Edin Fifić: Just try moving LED to the opposite power rail (to ground instead of V+).
• Edin Fifić: @Justme You're right, LED seems to be reversed.
• Edin Fifić: @ludicrous No, I don't think you should delete the question, but I would leave that up to the moderators. The point of SE is to share problems and solutions, and yours is a good example too. It shows how much we can go into details while it can be completely something else and just a simple mistake which makes it seem to not work after all the time, effort and knowledge invested.
• Arsenal: Just write your result up as an answer, it is perfectly fine to write an answer to your own question. And saying: the code is fine but I wired my circuit wrong (please describe with some detail) is also helpful.

Answer 1

SOLVED: Turns out that my microcontroller is working and the code is fine. The issue has to do with the circuit itself, I overlooked the fact that the LED is in reverse bias - so, of course, no current was passing through.

• Jens: Hint: The larger metal part inside the LED, holding the LED chip, is the cathode except it is an infrared LED.