Recommanded lockout chip pinout for new board designs ?
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Re: Recommanded lockout chip pinout for new board designs ?
Would another component (resistor, etc.) help connect the grounds without looping them?
Re: Recommanded lockout chip pinout for new board designs ?
A fuse (optionally self-resetting) would work, but does add a noticeable amount of cost, and I'm moderately confident that ground loops problems are not an issue here.
What is the problem with a ground loop? Current can flow through it when you didn't plan on it.
What is wrong with that? 1- thermal effects, 2- different ICs have different effective grounds, 3- lorentz force, and 4- inductive coupling
#1 is only a problem if your currents are humongous or your traces tiny, because of I²R.
#2 is mostly solved by using 5V digital logic. (Because you have to induce ~1V of error before things can start going wrong)
#3 requires comparatively large currents flowing through both the ground loop and something fragile, such as a bond wire. Unlikely to be an issue with a ROM.
#4 requires that the B field be pointing at the normal of some other loop. In the front loader, the cartridge is more-or-less right over the ground loop surrounding the 2A03 and 2C02, so I guess maybe you could do something here? But I've never heard of it.
What is the problem with a ground loop? Current can flow through it when you didn't plan on it.
What is wrong with that? 1- thermal effects, 2- different ICs have different effective grounds, 3- lorentz force, and 4- inductive coupling
#1 is only a problem if your currents are humongous or your traces tiny, because of I²R.
#2 is mostly solved by using 5V digital logic. (Because you have to induce ~1V of error before things can start going wrong)
#3 requires comparatively large currents flowing through both the ground loop and something fragile, such as a bond wire. Unlikely to be an issue with a ROM.
#4 requires that the B field be pointing at the normal of some other loop. In the front loader, the cartridge is more-or-less right over the ground loop surrounding the 2A03 and 2C02, so I guess maybe you could do something here? But I've never heard of it.
Re: Recommanded lockout chip pinout for new board designs ?
Back on the (original) topic, I wonder if it's possible to change the code in order to exchange LED, RST and DIN pins (pins 3, 6 and 7).
It looks like the RST pin doesn't use the AVR's build in reset, but instead does a software reset instead form a GPIO pin, probably for timing issues, so it should be possible to exchange those.
Looking at the source code, it would seem like a very easy mod to do, but I just want to ask to be double-sure.
Doing so will make it relatively easy to make a board that accepts both an authentic lockout chip, and an AVR clone, by positioning it at pins 5-12, which would be awesome.
Is a simple microcontroller pin really enough to supply current power a LED ?! Wouldn't you normally need an additional transistor to do something like that ? I guess I should check the AVR's datasheet.
EDIT : It seems it would even be possible to use either a normal CIC, or an AVR clone + a resistor + a LED, both using the same footprint (the unused extra pins of the CIC 3, 14, 15 and 16 are used to host the resistor and the LED when an AVR clone is used instead).
My (proposed) pinout is the following :
If using a real CIC, The solder pad should connect pins 14/15 to GND.
If using an Atmel, the older pad should connect pin 9 to Data Out.
In that case it's optional to add a resistor between pin 3 and 14, and a LED between pins 15 and 16 in order to have indication of the CIC's functioning (LED is "on" when the CIC is "working").
It looks like the RST pin doesn't use the AVR's build in reset, but instead does a software reset instead form a GPIO pin, probably for timing issues, so it should be possible to exchange those.
Looking at the source code, it would seem like a very easy mod to do, but I just want to ask to be double-sure.
Doing so will make it relatively easy to make a board that accepts both an authentic lockout chip, and an AVR clone, by positioning it at pins 5-12, which would be awesome.
Is a simple microcontroller pin really enough to supply current power a LED ?! Wouldn't you normally need an additional transistor to do something like that ? I guess I should check the AVR's datasheet.
EDIT : It seems it would even be possible to use either a normal CIC, or an AVR clone + a resistor + a LED, both using the same footprint (the unused extra pins of the CIC 3, 14, 15 and 16 are used to host the resistor and the LED when an AVR clone is used instead).
My (proposed) pinout is the following :
Code: Select all
----_----
Data Out <-x|P0.0 Vcc|--- 16 +5V
Data In 02 x->|P0.1 P2.2|x-x 15 Tied with pin 14
LED (seed) 03 x->|P0.2 P2.1|x-x 14 Solder pad to GND
GND (lock/key) 04 x->|P0.3 P2.0|x-x 13 Gnd
N/C 05 x- |Xout P1.3|<-x 12 VCC (unused GND input)
Clk in 06 ->|Xin P1.2|<-x 11 DIN (unused GND input)
Reset 07 ->|Rset P1.1|x-> 10 LED (Slave CIC reset)
Gnd 08 ---|Gnd P1.0|x-> 09 Solder pad to Dout (/Host reset)
---------If using an Atmel, the older pad should connect pin 9 to Data Out.
In that case it's optional to add a resistor between pin 3 and 14, and a LED between pins 15 and 16 in order to have indication of the CIC's functioning (LED is "on" when the CIC is "working").