Adding a WSI PSD813 to your MCU

5 December 1999

My recent work with the Waferscale psd813f1 device was initially disappointing.  I love the peripheral mix, but I hit a nasty problem regarding power-up of the device.  My LM2595 switcher power supply didn't bring +5 VDC up fast enough to suit the '813, and the device would lock up; no memory contents, unreliable peripheral states, other bad things.  I could make the device work properly if I used a battery supply, but the switcher just wouldn't work.  It wasn't a reset problem, either, since I was using a MC34064 reset chip and the 68hc11 never had a problem firing up.  When I discussed the problem with an engineer at WSI, he admitted that some of the devices show this behavior, and he suggested I add some circuitry to my power supply to force a fast rise.  I didn't like that solution, and I was ready to condemn the device as unusable and chalk the whole project up as a bad experience.

Further investigation leads me to believe that the problem is limited.  The '813 I was using was destroyed in a non-related phase of the project, and when I replaced the 90 nsec device with a 150 nsec device, the new device powered up perfectly.  The date code on the 90 nsec device is 9933.  This rang a bell; I think now that the 90 nsec device was an engineering sample of the latest mask, sent to me by WSI so I could play with the latest and greatest.  For now, the problem seems fixed, as the 150 nsec device works just fine.

31 October 1999

I've added a Waferscale psd813f1 device to my brand-new BOTBoard+, and the combination is dynamite!  My system now contains exactly two chips, the 68hc11e1 and the psd813f1; no glue chips whatsoever.  This tiny system sports 128KB of flash memory, 32KB of EEPROM, 2.5KB of static RAM, about 40 I/O lines of various types, and a wad of programmable logic that I can use to build shift registers, keypad scanners, and other cool subsystems.

The WSI web site offers a bunch of data sheets, app notes, and information; well worth checking out.  It also offers the DK800 development kit, a $99 package that includes a JTAG programming fixture, the PSDSoft compiler, lots of literature, and two free samples of your choice.  The kit is an outright steal for this price, especially since you can order two of the 'f1 chips with all of the above goodies in them.

I started with Marvin Green's BOTBoard+, assembled per his instructions and armed with a 68hc11e1 chip.  Next, I placed a 52-pin PLCC chip in the BB+'s prototype area and wired it up for the psd813f1.  This involves about 20 connections between the two chips, which only takes an evening or so to complete.  I also added a six-pin Molex KK-style male header, for use as a JTAG connector.  Here's a picture of the finished board (46K).

Next, I installed the PSDSoft compiler and used their easy-to-follow flowchart to develop the code for my psd813f1.  If you've never written programmable logic design (PLD) code before, PSDSoft makes the job about as easy as possible.  WSI includes templates for most of the common MCUs, including the 68hc11.  Your job mainly consists of removing all of the extra features they added to their template, trimming it back to only the elements you need.

I built a very simple design, using just 32K of flash ($8000 to $ffff) and 24K of EEPROM ($2000 to $7fff).  I also put the static RAM from $200 to $9ff, just beyond the 68hc11e1's 512 bytes that ends at $1ff.  I also placed the psd813f1's I/O registers (a block of 256 bytes) from $1100 to $11ff.  Note that you can move these resources wherever you want in the system's memory map, based on the your design.  The psd813f1 even sports an 8-bit paging register, allowing you to break on-chip and off-chip memory into 256 different pages.

Once that was done, I compiled my code file.  Next, I merged my design with some 68hc11 object code I had laying around.  This is where your .s19 files, created by a C compiler or by SBasic, get mixed in.  I needed to know where in the code space my program was assigned to run, since the merging utility must resolve addresses properly.

Finally, I plugged the JTAG programming connector into my BB+, applied power, and started a JTAG download.  Within a minute or two, the download was complete.  When I used pcbug11 to check my board, the 2.5K of static RAM appeared just where it belonged.

Bottom line:  Get the DK800 development kit and start playing with some serious memory expansion.  The psd813fx chips turn any little 68hc11 system into a BIG machine.

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