T5577 Writable / Programmable Transponder Compatible Cards & Fobs
The T5577 (ATA5577C) is a 256-bit rewritable 125 kHz transponder IC that can be programmed to emulate virtually any unencrypted LF proximity format, making it the universal clone target and spare-card solution for legacy 125 kHz access control systems.
Originally developed by Atmel and now produced by Microchip Technology as the ATA5577C, the T5577 stores 256 bits of EEPROM user data with configurable modulation, data rate, and encoding to replicate the RF signature of any standard 125 kHz proximity format. American Key Cards supplies T5577 blanks in clamshell, ISO PVC, and key-fob form factors — as unprogrammed blanks or pre-programmed to your specified format and facility code range using verified programming equipment.
T5577 Writable / Programmable Transponder specifications
- Brand / OEM
- Microchip Technology Inc. (ATA5577C)
- Technology
- Passive RFID — multi-protocol writable transponder
- Frequency
- 125 kHz
- Chip
- ATA5577C (formerly Atmel T5577); 256-bit EEPROM user memory + 32-bit config block + 32-bit password block; 100,000+ write cycles; supports data rates RF/2 through RF/128; configurable modulation (ASK/FSK/PSK/Manchester/Biphase); Wiegand output emulation
- Bit formats
- User-programmable — emulates EM4100, EM4102, HID Prox H10301 (26-bit Wiegand), Indala, AWID, Kantech ioProx, DoorKing DKProx, SecuraKey Radio Key, Farpointe Pyramid, FDX-B, Noralsy, Keri, Jablotron, Honeywell NexWatch, Nedap, Presco, Viking, and others
- OEM part numbers
- ATA5577C, T5577
Our compatible T5577 Writable / Programmable Transponder credentials
American Key Cards manufactures non-OEM credentials engineered to work with your existing Microchip Technology (formerly Atmel) readers — no hardware changes, encoded to your facility code and card-number range.
Can T5577 Writable / Programmable Transponder cards be copied?
T5577 Writable / Programmable Transponder is an open format, so a compatible card can be produced from your facility code and card number. We don't copy individual cards on request — we manufacture new, correctly-encoded credentials for systems you own or manage.
T5577 is explicitly designed for cloning and emulation of 125 kHz formats — it is the standard clone-target chip for nearly all LF proximity credentials. Because it can emulate virtually any unencrypted 125 kHz format, a lost or stolen T5577 programmed to a valid credential is indistinguishable from the original. Use only where 125 kHz is already the site standard; consider upgrading to encrypted 13.56 MHz for new installations.
Where T5577 Writable / Programmable Transponder is used
- Cloning existing 125 kHz cards to spare blanks
- Replacement credentials for formats no longer in OEM production
- System testing and access control commissioning
- Proxmark3 / Flipper Zero research and security assessment
- Universal spare stock that can be programmed to any installed 125 kHz format
Compatible readers
Related formats
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HID Prox H10301 (Standard 26-Bit)
The HID H10301 26-bit format is the most widely deployed proximity card format in North America, used on millions of doors across commercial and residential buildings.
View compatible cardsAWID 26-Bit
AWID 26-bit is a 125 kHz proximity format outputting standard Wiegand 26-bit data (facility code 1–255, card number 1–65,535) via the AWID proprietary air interface, widely used in legacy commercial and residential access control systems.
View compatible cardsIndala FlexPass 26-Bit
Indala FlexPass 26-bit is a 125 kHz proximity card format using PSK modulation — architecturally distinct from HID Prox — with Wiegand output supporting 255 facility codes and up to 65,535 card numbers per site.
View compatible cardsT5577 Writable / Programmable Transponder — FAQ
What formats can a T5577 card emulate?
The T5577 can be programmed to emulate virtually any unencrypted 125 kHz format including EM4100, HID Prox H10301 (26-bit), Indala, AWID, Kantech ioProx, DoorKing DKProx, SecuraKey Radio Key, Farpointe Pyramid, FDX-B, and many others — using a Proxmark3, Flipper Zero, or compatible RFID programmer.
How many times can a T5577 card be reprogrammed?
The ATA5577C supports over 100,000 write cycles, making it effectively reusable for the life of an access control system.
Are T5577 cards detectable as clones by readers?
No — standard 125 kHz proximity readers have no way to distinguish a T5577 emulating a format from an original OEM card in that format. The RF signal and data stream are identical.