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Topic: Identifying some zyxel p660hw-d1 parts..

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Post #1
alberich2k5
20 Mar 2011, 22:08

Hello!

I'm new on this forum but not new at linux worl.
I got an old p660HW-D1 zyxell router and I thought on trying to make openwrt boot on that router.

I opened the device and start looking at its chips. My question comes when I tried to identify the ram and flash size.

the chips are:
- MX29LV160CBTC-70G for the flash. I think it's 2MB, although the datasheet says 1 x 16M 2X 8M.
- W9812G6IH-75, which I think it's a 16MB SDRAM.

I got the datasheets, and i could not understand how to get the size of the chip. For example, this datasheet  http://winbond-usa.com/products/winbond … 2G6IHa.pdf says 2M x 4 Banks x 16 bit.

Can anyone help me?

thanks!!
Alberich

Post #2
asier
10 Apr 2011, 13:19

Hi Alberich,

I guess you know it by now, but you got the sizes right. Basically, the Flash memory array size is 2MB in total and can be accessed either as a 1Mx16bit memory or as a 2Mx8bit memory. I guess this device uses the 1Mx16bit configuration.

Regarding the SDRAM memory, it has 4 banks (memory arraies) of 2Mx16bit each, which is the same as saying 8Mx16bit or 16Mx8bit. To calculate these values you need to note the table in the page 5 of the datasheet. Here, it tells you the device has 12 address pins (A0 - A11), however, the description tells you that pins A0-A11 are used to decode the targeted bank's row address (see block diagram in page 6) and that pins A0-A8 are used to decode the column address. In a way, it would be like saying that pins A0-A11 are used to select a page within the bank, and then pins A0-A8 are used again to select a given address within that page.

This is, pins A0-A8 are shared to get the actual target address in the bank. As a result, a total of 21 address bits are actually used to generate the target address, which gives you the 2M addresses. Each address is 16-bit wide, which is the data bus width. Finally, pins BS0 and BS1, see page 5, are used to select one of the four available banks. Hence, the 8Mx16bit or 16Mx8bit.

I hope this helps.

Cheers,
Asier

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