6502, 65SC12, 65C102, huh?

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jregel
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6502, 65SC12, 65C102, huh?

Post by jregel » Sun Mar 10, 2019 10:50 pm

jregel wrote:
Sun Mar 10, 2019 10:50 pm
I’ve been doing some reading up around the different CPUs found in the different BBC models and would like to check my understanding is correct:

BBC Model A and B

Original BBC Model B has a MOS 6502A (NMOS).

External 6502 Second Processor

The external 6502 Second Processor uses a Rockwell 65C02 (CMOS) version which includes bug fixes, eight new instructions (BRA, PLX, PLY, PHX, PHY, STZ, TRB, TSB), plus four additional Rockwell-only instructions (BBR, BBS, RMB, SMB), and two new addressing modes (“Indexed Absolute Indirect” and “Indirect Zero Page”).

The BASIC II assembler doesn’t support use of the 12 additional instructions or addressing modes(?).

BBC Master and Compact

The Master uses a Rockwell 65SC12 CMD/GTE G65SC12, which adds the eight new instructions, and addressing modes, from the second processor’s 65C02. The Rockwell-specific instructions are not supported.

The BASIC IV assembler adds support for the eight additional instructions of the 65C02, and two of the Rockwell-only instructions (BBR and BBS).

BBC Master Turbo

The Master Turbo co-processor has a Rockwell 65C102 with, presumably the same features as the Master’s 65SC12.

Questions

Does anyone know what the difference is between the Master’s 65SC12 and the co-processor 65C102?

Does the 6502 emulation provided by the PiTubeDirect support the Rockwell instructions?

Thanks!
Last edited by jregel on Tue Mar 12, 2019 3:09 pm, edited 1 time in total.
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Re: 6502, 65SC12, 65C102, huh?

Post by dp11 » Sun Mar 10, 2019 11:03 pm

jregel wrote:
Sun Mar 10, 2019 10:50 pm
Does the 6502 emulation provided by the PiTubeDirect support the Rockwell instructions?
Yes it does.

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tricky
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Re: 6502, 65SC12, 65C102, huh?

Post by tricky » Mon Mar 11, 2019 8:03 am

Did all of the B+ have Rockwell R6512AP and which BASIC?

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Re: 6502, 65SC12, 65C102, huh?

Post by jregel » Mon Mar 11, 2019 6:44 pm

I believe the B+ has a 2Mhz Rockwell 6512A.

I'd assume it runs BASIC II, since it precedes the Master...?
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hoglet
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Re: 6502, 65SC12, 65C102, huh?

Post by hoglet » Mon Mar 11, 2019 7:13 pm

One clarification:
jregel wrote:
Sun Mar 10, 2019 10:50 pm
The Master uses a Rockwell 65SC12, which adds the 12 new instructions, and addressing modes, from the second processor’s 65C02.
Both my Masters use a CMD/GTE G65SC12, which doesn't include RMB/SMB/BBR/BBS.

Datasheet is here:
http://archive.6502.org/datasheets/cmd_ ... family.pdf

Column's x7 and xF are blanks.

(And I'm pretty sure the Dormann 65C02 tests for RMB/SMB/BBR/BBS fail, so it's not just a incorrect documentation)

Dave
Last edited by hoglet on Mon Mar 11, 2019 7:13 pm, edited 1 time in total.

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Re: 6502, 65SC12, 65C102, huh?

Post by SarahWalker » Mon Mar 11, 2019 8:56 pm

tricky wrote:
Mon Mar 11, 2019 8:03 am
Did all of the B+ have Rockwell R6512AP and which BASIC?
IIRC the B+'s 6512 is just an NMOS 6502 with different clock inputs and not a 65c12 with new instructions. As a result it runs BASIC II.

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Re: 6502, 65SC12, 65C102, huh?

Post by jregel » Mon Mar 11, 2019 9:09 pm

dp11 wrote:
Sun Mar 10, 2019 11:03 pm
jregel wrote:
Sun Mar 10, 2019 10:50 pm
Does the 6502 emulation provided by the PiTubeDirect support the Rockwell instructions?
Yes it does.
Thanks for the clarification!
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Re: 6502, 65SC12, 65C102, huh?

Post by 1024MAK » Tue Mar 12, 2019 2:49 am

SarahWalker wrote:
Mon Mar 11, 2019 8:56 pm
tricky wrote:
Mon Mar 11, 2019 8:03 am
Did all of the B+ have Rockwell R6512AP and which BASIC?
IIRC the B+'s 6512 is just an NMOS 6502 with different clock inputs and not a 65c12 with new instructions. As a result it runs BASIC II.
Yes, the Rockwell NMOS 6512 has the same instruction set as the NMOS 6502. The 6502 has an on board clock generator circuit, whereas the 6512 needs an external two phase clock generator. The 6512 does have a data bus enable pin so that external circuits can take control of the databus. See the Rockwell datasheet here on 6502.org :wink:

Mark

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Re: 6502, 65SC12, 65C102, huh?

Post by jregel » Tue Mar 12, 2019 3:02 pm

hoglet wrote:
Mon Mar 11, 2019 7:13 pm
One clarification:
jregel wrote:
Sun Mar 10, 2019 10:50 pm
The Master uses a Rockwell 65SC12, which adds the 12 new instructions, and addressing modes, from the second processor’s 65C02.
Both my Masters use a CMD/GTE G65SC12, which doesn't include RMB/SMB/BBR/BBS.

Datasheet is here:
http://archive.6502.org/datasheets/cmd_ ... family.pdf

Column's x7 and xF are blanks.

(And I'm pretty sure the Dormann 65C02 tests for RMB/SMB/BBR/BBS fail, so it's not just a incorrect documentation)

Dave
Thanks, I'll edit the original post to avoid confusion. There's no better confirmation than visually checking the computer!

On re-reading the documentation (Dabhand Guide to the Master Operating System), it suggests that only the 6502 second processor and Master Turbo co-processor use Rockwell CPUs, so it sounds like the Rockwell-specific instructions should generally be avoided (and reasonably explains why the assembler was expanded to support the eight new 65C02 instructions, but not the Rockwell-specific instructions).
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