Atari 800XL 6520A PIA chip replacement

[unebonnevie]

Hi,

 

I believe my 800XL goes dead because of a dead PIA.  I get the blank screen.  Swapped out other chips with working ones, and those chips are fine.  The only one left is the PIA, but the working 800XL that I use to debug the dead 800XL does not its PIA socketed.  I have a strong feeling (yes the force is strong on this one), the dead 800XL is due to a bad PIA chip.  I was doing some SIO HW project, and probably caused it to die.

 

So, I saw that WDC (Western Design Center) has the PIA below and it's compatible with the Rockwell PIA that is used by my dead 800XL.  The only thing I am not sure of is the WDC says NMOS compatible.  Does anyone know if the Atari 800XL's Rockwell PIA is NMOS or CMOS?

 

W65C21N6TPG-14

Peripheral Interface Adapter NMOS Compatible / Plastic Dual-In-Line, 40 pins, RoHS and Green Compliant

 

Mouser stocks it at https://www.mouser.com/ProductDetail/Western-Design-Center-WDC/W65C21N6TPG-14?qs=%2Fha2pyFaduifD1gf44hwy5ejokbLHUq8bOouCmEsViCPIGu8FqTGdA%3D%3D

 

Thank you!

Edited November 14, 2020 by unebonnevie

[TGB1718]

According to the datasheet, it's a low power replacement for the following and the 800XL uses a 6520A :-

 

https://www.mouser.co.uk/datasheet/2/436/w65c21-661.pdf

 

• Low Power CMOS N-well silicon gate technology

• The W65C21N is plug replacement of NMOS and CMOS 6521 and 6821 devices with current limiting resistors

• The W65C21S is lower power, faster and direct drive outputs with no current limiting resistors.

• High speed/Low power replacement for Motorola/Rockwell/AMI/MOS Technology/MOSTEK/HITACHI/ ST Microelectronics/GTE/CMD 6520, 6521, 6820, 6821 PIA’s

• Two 8-bit bidirectional I/O ports with individual data direction control.

• Automatic “Handshake” control of data transfers • Two interrupts (one for each port) with program control

• Static to 14MHz operation, with high speed Port A, CA2 outputs.

• Industrial temperature range

• 40 Pin Plastic DIP and 44 Pin Plastic PLCC versions

• 5 volt ± 10% supply requirements

• Compatible with the 65xx and 68xx family of microprocessors

 

So should be a good replacement

 

 

[Rybags]

PIA's only involvement with the SIO port is /Command, Motor Control and the /IRQ and /Proceed lines.

Much of the rest goes to Pokey.

[thorfdbg]

5 hours ago, unebonnevie said:

Hi,

 

I believe my 800XL goes dead because of a dead PIA.  I get the blank screen.  Swapped out other chips with working ones, and those chips are fine.  The only one left is the PIA, but the working 800XL that I use to debug the dead 800XL does not its PIA socketed.  I have a strong feeling (yes the force is strong on this one), the dead 800XL is due to a bad PIA chip.  I was doing some SIO HW project, and probably caused it to die.

 

So, I saw that WDC (Western Design Center) has the PIA below and it's compatible with the Rockwell PIA that is used by my dead 800XL.  The only thing I am not sure of is the WDC says NMOS compatible.  Does anyone know if the Atari 800XL's Rockwell PIA is NMOS or CMOS?

 

W65C21N6TPG-14

Peripheral Interface Adapter NMOS Compatible / Plastic Dual-In-Line, 40 pins, RoHS and Green Compliant

 

Mouser stocks it at https://www.mouser.com/ProductDetail/Western-Design-Center-WDC/W65C21N6TPG-14?qs=%2Fha2pyFaduifD1gf44hwy5ejokbLHUq8bOouCmEsViCPIGu8FqTGdA%3D%3D

 

Thank you!

It is possible because the PIAs are responsible for banking the ROM or Basic ROM in, but something else could be dead as well. I had a dead 800XL where the delay line and the MMU broke.

The PIAs in the original 800XL are NMOS parts, but that is only a fabrication detail, a CMOS part would work as well - only the input/output levels need to be compatible.

[unebonnevie]

1 hour ago, thorfdbg said:

It is possible because the PIAs are responsible for banking the ROM or Basic ROM in, but something else could be dead as well. I had a dead 800XL where the delay line and the MMU broke.

The PIAs in the original 800XL are NMOS parts, but that is only a fabrication detail, a CMOS part would work as well - only the input/output levels need to be compatible.

Thanks for the info.  I'll WDC's PIA and give it a try.  Their PIA (the part mentioned in the OP) is 100% compatible with Rockwell 6520A, which the Atari uses.  It's much cheaper and is 100% new then buying on eBay of 40-year-old part.

 

How do you diagnose you 800xl's delay line and MMU broke?  (I am able to locate the MMU on my 800's XL motherboard.)

 

Thank you!

[thorfdbg]

2 hours ago, unebonnevie said:

How do you diagnose you 800xl's delay line and MMU broke?  (I am able to locate the MMU on my 800's XL motherboard.)

Well, as always: Replace by a known good part.

 

[TGB1718]

Have a look at the circuit diagram on page 3, it has the voltage levels on each pin, would also help if you have a scope.

 

 

 

Atari_800XL_Sams_Computerfacts_Technical_Service.pdf

[unebonnevie]

8 hours ago, TGB1718 said:

Have a look at the circuit diagram on page 3, it [the memory management chip] has the voltage levels on each pin, would also help if you have a scope.

 

 

 

Atari_800XL_Sams_Computerfacts_Technical_Service.pdf 29.89 MB · 2 downloads

Thank you VERY much for the attachment and tip.

Edited November 15, 2020 by unebonnevie

[Beeblebrox]

On 11/14/2020 at 10:42 AM, TGB1718 said:

According to the datasheet, it's a low power replacement for the following and the 800XL uses a 6520A :-

 

https://www.mouser.co.uk/datasheet/2/436/w65c21-661.pdf

 

• Low Power CMOS N-well silicon gate technology

• The W65C21N is plug replacement of NMOS and CMOS 6521 and 6821 devices with current limiting resistors

• The W65C21S is lower power, faster and direct drive outputs with no current limiting resistors.

• High speed/Low power replacement for Motorola/Rockwell/AMI/MOS Technology/MOSTEK/HITACHI/ ST Microelectronics/GTE/CMD 6520, 6521, 6820, 6821 PIA’s

• Two 8-bit bidirectional I/O ports with individual data direction control.

• Automatic “Handshake” control of data transfers • Two interrupts (one for each port) with program control

• Static to 14MHz operation, with high speed Port A, CA2 outputs.

• Industrial temperature range

• 40 Pin Plastic DIP and 44 Pin Plastic PLCC versions

• 5 volt ± 10% supply requirements

• Compatible with the 65xx and 68xx family of microprocessors

 

So should be a good replacement

 

 

Hi

Bit of a Necrobump but I am just looking at getting one or two PIA IC's for spares and found this thread. It mentions Mouser.co.uk sell the two models (W65C21N and W65C21S). Is it best to go with the faster, low power one (W65C21S) for 600XL and 800XL A8s? thanks 

 

https://www.mouser.co.uk/c/?q=w65c21

 

[Kyle22]

I hope I have it working now. Someone please call me.

I hope I got the port forward right. I forwarded Port 10001 to port 6502 pointed @ the FujiNet.

What port is for the modem?

I was messing w/ my router all day.

 

Edited October 16, 2021 by Kyle22
one too many zeros.