CASIO PV-7 to 16Kb RAM

By wernerkai

Champion (357)

wernerkai's picture

29-05-2013, 05:15

Hi, folks.

The CASIO PV-7 has only 8Kb of RAM from &HE000 to &HFFFF in Slot 0.

I've made some tests with an OR-216 CASIO 16Kb RAM cartridge, an Epcom/Sharp HB-4100 64Kb RAM cartridge and the ACVS/CIEL slotexpander. And also three FDD interfaces. One I/O port-mapped, and two memory-mapped.

The FDD interface doesn't boot with only 8Kb of RAM.

The OR-216 puts 16Kb of RAM in page 2, from &H8000 to &HBFFFF. But even with the cartridge alone in slot 1, the RAM is splitted, and the system recognizes only the top 8Kb.

So, if you connect the FDD interface and the 64Kb RAM cartridge through the slotexpander, the FDD will boot and load MSX-DOS. I found MSXMEM2.BAS doesn't recognize the 8Kb RAM at Slot 0 page 3:

CASIO PV-7 with 8kb RAM

In another PV-7 (I have more than one), I've piggybacked a chip of 8Kb SRAM over the main RAM:

Picture 1
Picture 2

The main RAM is the uPD4168C-20. I put there an 6264-like. I didn't connect the pin 1(NC) and put a 74LS04 to invert the CS signal from pin 26, which I found to be A13 from address bus.

After that, the MSX shows 16Kb of RAM after boot, and it can boot all FDD interfaces. With the OR-216 it shows 32 Kb of RAM. But with 16Kb and 32 Kb it can't load MSX-DOS.

Here is the result from MSXMEM2.BAS:
PV-7 With 16Kb + 16Kb from OR-216

By hacking with the multimeter and the oscilloscope, I found the following:

Pin 1 of uPD4168C-20 RAM (/RFSH) is connected to pin 3 of engine MB64H131.
Pin 20 of uPD4168C-20 RAM (/CE) is connected to pin 4 of engine MB64H131.
Pin 22 of uPD4168C-20 RAM (/OE) is connected to /RD signal from Z80.
Pin 26 of uPD4168C-20 RAM (CS) is connected to A13 signal from Z80.
Pin 27 of uPD4168C-20 RAM (/WE) is connected to /WR signal from Z80.

Pin 20 of 32Kb PROM (/CE) is connected to pin 5 of engine MB64H131.
Pin 22 of 32Kb PROM (/OE) is connected to /RD signal from Z80.

/SLTSL1 is the pin 61 of engine MB64H131, which also goes to the cartridge slot.
/SLTSL2 is the pin 62 of engine MB64H131.

I didn't found /SLTSL3...

This week, I bought a CASIO OR-208 8Kb RAM cartridge. But it's still in Japan waiting for shipping. I'm very curious because...

In that Korean blog post, they show the pinout of KB-10 connector, and there are not slot selection signals. Maybe it's the same with KB-7 ? How the two extra slots work without /SLTSL signals ?

How would the PV-7 manage the original 8Kb of RAM in slot 0, plus the 8Kb of RAM in another slot ?

Is this feature non standard ?

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By gdx

Prophet (2661)

gdx's picture

19-09-2014, 05:17

Better late than never. LOL!

A MSX with 8KB is standard but it is become quickly obsolete. A 8KB expansion is possible but unusual and not easy to manage. I know no software that considers Slots with 8KB. I think only Slots with 16KB are considered.

In general, the developers make a routine to find a Slot that contain a RAM whose size allows to run their software. They do not often take into account the scattered RAM.

PS: You can add Sound IN pin on the expansion Bus:
http://sions-papa.blogspot.jp/2014/08/msx-pv-7pv-161984198x....

By Tabajara-Labs

Expert (91)

Tabajara-Labs's picture

23-11-2014, 14:34

Pinout of the expansion connector on the PV7:
PV-7 MSX MSX PV-7
1 +5V GND 2
3 +5V GND 4
5 1 2 6
7 3 6 8
9 7 8 10
11 9 nc 12
13 11 12 14
15 13 14 16
17 15 nc 18
19 17 18 20
21 19 20 22
23 21 22 24
25 23 24 26
27 25 26 28
29 27 28 30
31 29 30 32
33 31 32 34
35 33 34 36
37 35 36 38
39 37 38 40
41 39 40 42
43 41 42 44
45 sndin pv nc 46
47 +5V GND 48
49 +5V GND 50

Is there a better way to build a table here?

By Grauw

Enlighted (7967)

Grauw's picture

23-11-2014, 14:51

Tabajara-Labs wrote:

Pinout of the expansion connector on the PV7:

PV-7	MSX	MSX	PV-7
1	+5V	GND	2
3	+5V	GND	4
5	1	2	6
7	3	6	8
9	7	8	10
11	9	nc	12
13	11	12	14
15	13	14	16
17	15	nc	18
19	17	18	20
21	19	20	22
23	21	22	24
25	23	24	26
27	25	26	28
29	27	28	30
31	29	30	32
33	31	32	34
35	33	34	36
37	35	36	38
39	37	38	40
41	39	40	42
43	41	42	44
45	sndin pv	nc	46
47	+5V	GND	48
49	+5V	GND	50

Is there a better way to build a table here?

use [ code ] [ /code ] around it

By Tabajara-Labs

Expert (91)

Tabajara-Labs's picture

01-12-2014, 02:41

I just confirmed with the logical analyser: There is no /sltsel3 on the PV7 board.

Firstly I thought the output of the MB64H131 was a binary nibble. Two pins output, to 4 selections. So I put the logic analyser on it to see how it works.

(top: CH0 -> Pin 61. CH1 -> Pin 62)

Seems to work, but zooming on the signal...
(top: CH0 -> Pin 61. CH1 -> Pin 62)

So, there is the prove. The pins 61 and 62 of the MB64H131 really are /sltsel1 and /sltsel2

Of course, I probed around the non used pins, and tried to find a corresponding signal. No cigar.

Next step: create a small CPLD with the slot select logic, so I can select an internal slot 3 to put 64K of RAM B-)

By MSXPro

Resident (48)

MSXPro's picture

01-12-2014, 05:54

Here an better table to understand PV-7 expansion connector:

1	+5V		GND	2
3	+5V		GND	4
5	/CS1		/CS2	6
7	/CS12		/RFSH	8
9	/WAIT		/INT	10
11	/M1		N.C.	12
13	/IORQ		/MREQ	14
15	/WR		/RD	16
17	/RESET		N.C.	18
19	A9		A15	20
21	A11		A10	22
23	A7		A6	24
25	A12		A8	26
27	A14		A13	28
29	A1		A0	30
31	A3		A2	32
33	A5		A4	34
35	D1		D0	36
37	D3		D2	38
39	D5		D4	40
41	D7		D6	42
43	GND		CLOCK	44
45	SOUNDIN		N.C.	46
47	+5V		GND	48
49	+5V		GND	50

By l_oliveira

Hero (519)

l_oliveira's picture

20-06-2015, 15:36

uPD4168C-20 = PSRAM (Pseudo SRAM)

It needs refresh because internally it works like DRAM.

By gdx

Prophet (2661)

gdx's picture

21-06-2015, 07:37

The page of the link that I given above shows also that it is possible to replace the PSRAM by an SRAM. Thus it's easier to expand to 16 KB (and certainly 32 KB).

The used SRAM is the LC36256AL-10 (32KB). Only two pins are different (1 & 26).
The refresh signal is unused by SRAM. The SRAM HY62256A and the LC36256AL are similar.

A LC36128L would be perfect to expand to 16 KB. Only the pin 26 is different. This pin must be connected to A13.

By l_oliveira

Hero (519)

l_oliveira's picture

21-06-2015, 07:44

Some PSRAMs are annoying to use, because you need to OR the /OE signal with /RFSH so the chip get refresh signal while it's not being accessed by the computer.

For example because there are spare pins, the 6564 (8Kb) and 658128 (128Kb) PSRAMs take refresh on their pin 1. But 65256 and 658512 types do need the OR with /OE because they have no spare pins. That make the circuit a bit more complex.

Fortunately for us the SRAM chips got a lot cheaper and because of that PSRAM chips are now "moot point" and unnecessary complexity. But here I had a couple of them lying about so I had them used on my MSX. I made 1MB of internal mapper for my MSX2 modded VG8020.

By gdx

Prophet (2661)

gdx's picture

31-07-2016, 12:39

Any news about OR-208 and PV-7 slots pinout?

My MSX profile