I/O ports are quite messy... (Detect OpenMSX) | MSX Resource Center (Page 3/5)

Champion (328)

08-04-2023, 02:41

Like the Philips machines 8250/8280, superimpose etc, running S3527 and have a clockchip!!!
I could not find anything about clockchip in S3527 manual

By Grauw

Ascended (10767)

08-04-2023, 02:46

gdx wrote:

@Grauw, What is the machine code for OUT (BC),R? Is there IN R,(BC) or equivalent?

IN r,(BC) = ED 40 + r*8
OUT (BC),r = ED 41 + r*8

See Z80 manual page 296 and 307.

By gdx

Enlighted (6207)

08-04-2023, 02:47

Thanks. I thought these codes were for IN B,(C) and OUT (C),B.

Turbo R has no VDP mirror.

By Grauw

Ascended (10767)

08-04-2023, 03:00

gdx wrote:

Thanks. I thought these codes were for IN B,(C) and OUT (C),B.

And A,(C), C,(C), D,(C), E,(C), H,(C) and L,(C). (Since I wrote + r*8.) But yes, they are the same. BC is output to A0-A15 for all of these.

Accumulator wrote:

Like the Philips machines 8250/8280, superimpose etc, running S3527 and have a clockchip!!!
I could not find anything about clockchip in S3527 manual

Clock chip is an MSX2 feature which did not exist for MSX when S3527 was released and therefore it does not offer any functions for it. The clock chip is the Ricoh RP5C01 and its chip select is not decoded by the S3527 but by separate decoding logic, as can be seen on the NMS 8250 service manual.

By Accumulator

Champion (328)

08-04-2023, 02:55

@gdx,
Maybe it shows not as a mirror, but if you address the possible mirrored ports?
it can be as simple as :
xor a
; or 2
out (&H9d),a
ld a,9+128
out (&H9d),a
ret
see if something changes...

By Accumulator

Champion (328)

08-04-2023, 02:58

As far as I could remember, it is possible to set password, message at boot.
This is done by clockchip , or am i mistaken...

By Grauw

Ascended (10767)

08-04-2023, 02:59

Yes, it’s an MSX2 feature. MSX1 has no clock chip.

By Accumulator

Champion (328)

08-04-2023, 03:54

So, does the NMS 8250/8280 have a clock chip? Separate clock chip?
How it this managed?

Just checked OpenMSX with NMS8250 as NMS8280 is not available.
Ports B4 and B5 are available, BASIC like SET PASSWORD and SET PROMPT are available and working.
Looks like there is a clock chip available..

Just checked the service manual and indeed there is an additional RPC501 chip used.
Even with S-3527 there is a clock chip at #B4H and #B5H

By gdx

Enlighted (6207)

08-04-2023, 11:02

Grauw wrote:

gdx wrote:

@Grauw, What is the machine code for OUT (BC),R? Is there IN R,(BC) or equivalent?

IN r,(BC) = ED 40 + r*8
OUT (BC),r = ED 41 + r*8

See Z80 manual page 296 and 307.

I just tried ED 40 with SHEM on turbo R Z80/R800 and I get IN B,(C) not IN r,(BC). Next byte, B and R registers have no effect.

By ToriHino

Paladin (855)

08-04-2023, 11:44

Indeed ED 40 is IN B,(C), adding 8 to the second byte (so ED 48) will give IN C, (C), adding an additional 8 (so ED 50) will give IN D, (C), etc..... And as mentioned earlier this actually is IN B, (BC) since BC is output to A0-A15