Teardown Tuesday: Credit Card Reader

July 26, 2016 by Alex Udanis

Ever wonder what's inside a credit card machine? In this Teardown Tuesday, we are going to take a look at one!

Today, nearly all business accept credit cards. Ever wonder what's inside a credit card machine? In this Teardown Tuesday, we are going to take a look at one!


Credit Card Machine Teardown

The Verifone credit card machine


In this teardown, we are looking at a relatively old Verifone credit card machine, a model 3730. This is a machine that has a built-in receipt printer and was made far before chips were on cards in the USA.


Circuit Boards

There are two circuit boards in this credit card machine.

The bottom circuit board contains the phone line connections and the power connection. The bottom PCB is a two-sided PCB with green solder mask and white silkscreen. The board is made primarily of surface mount components with the backup battery and power connector being through-hole. This PCB has several unpopulated components including a BGA.


Credit Card Machine PCB

The bottom PCB


The top PCB contains the microcontroller, keypad, and display. Just like the bottom PCB, this circuit board has green solder mask, white silkscreen, and is comprised primarily of surface mount components. This PCB has quite a few unpopulated components, such as LED footprints to provide illumination to the keypad. This could be the case because this PCB is used in a variety of card reader models.


The Top Credit Card Machine PCB

The topside of the top PCB


Joining the two PCBs together are several connectors. There are two zebra connectors and a 60-pin fine pitch Wieson board-to-board connector. These three connectors give 78 connections between the two PCBs.


Zebra Board to Board Connector

One of the zebra connectors


Custom IC


Custom Verifone IC

The custom Verifone IC


On the bottom PCB, there is a custom IC. This IC is marked as VERIFONE 08233-01-R Rev.A and is in a BGA package. Zero information about this IC is available online. However, purely speculating based on its location on the PCB, it most likely handles the secure data transfer of the credit card information.




Modem IC

The modem IC


In order to transmit the data, the credit card machine relies on a modem on the bottom PCB. The machine uses a Conexant CX81801. This IC is intended for applications such as POS terminals, security, remote site management, and any other application that requires robust dial-up connectivity—making it ideal for an application like this. This IC is packed full of tons of features. Take a look at its datasheet (PDF) for all of the details!




The Samsung S3C24 SOC

The Samsung microprocessor


At the heart of the credit card machine is a Samsung S3C2410AL-20 Microprocessor in a 272 FBGA package. This 32-bit microprocessor is based on an ARM920T core and features a 200MHz clock speed.

Samsung intended for this IC to be used in either hand-held devices or high-performance applications that still need to be low-power and inexpensive.

This microprocessor contains many additional peripherals to reduce the component count such as an LCD controller, a real time clock, and 16KB of instruction memory. In order to keep an accurate time even if the device was powered off, a CR23540 cell is used to provide backup power.


Battery Backup

The battery backup




The low power RAM


Located on the top board is the RAM for the microprocessor in a 48 BGA package. This is a Samsung component K6F8016U6D-XF55. This IC is a SRAM that contains 512K x16 bit of memory and is “Super Low Power”.


Card Reader


Credit Card Reader Head Three Track

The card reader head


In order to read information from the credit card, a magnetic head is used. This head is similar to those found in cassette players.

Credit cards typically store information on multiple ‘tracks’. In most cases, two tracks are used. On these tracks, information such as the Primary Account Number (PAN), Name (NM), Expiration Data (ED), and Service Code (SC) are stored. The magnetic head used in this credit card reader has the ability to read three tracks, but typically the third track is not used.

For more information regarding how data is stored on these tracks, read up on the IEC 7813 standard.


Receipt Printer


Thermal Print Head

The card reader head


This credit card machine contains an internal receipt printer. This printer uses a printing method called thermal printing. Thermal printing relies on a thermal head that contains many separate heating elements. The microcontroller controls when each segment is turned on. The printhead is mounted on a ceramic backing.


IR Paper Sensor

The IR paper sensor


To feed the paper through the thermal printing head, a rubber roller moves the paper along. The roller is connected through a set of gears to a motor. In this case, a stepper motor is used rather than a conventional DC motor due to the extra precision that can be achieved.

This credit card reader also has the ability to detect if it has run out of receipt paper. There is a small IR emitter and receiver that detects the light reflected off of the white paper. This sensor is mounted to a flexible circuit board.



Discrete credit card machines like this are becoming rare these days. Instead, card readers are typically more tightly integrated with the point of sale system. These new integrated systems reduce complexity, increase efficiency, and reduce cost.

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