How can I shift out a 40bit word serially?

PanchoFrank

Hello Group,
I'd like to use a BS2 to generate·two 40bit words needed to serially program a National Semiconductor PLL chip.
I know how to send 7 or 8 bit words using the serout command, but·don;t yet understand how to store and then shift out this long serial stream.
Help is appreciated.
PanchoFrank

Newzed

Stamps can not handle 40-bit words - only 16-bit words.

Sid

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·

PJAllen

How many bits per second?· Maybe you can do this by spoon-feeding --·by selected HIGHs/LOWs timed with PAUSEs.· This would be very easy to do with an SX (using SX/B, you can time micro-second pulses using PAUSEUS.)

HIGH 0
PAUSE 1
LOW 0
PAUSE 1
HIGH 0
PAUSE 1
HIGH 0
PAUSE 1
...

Tracy Allen

This will use SHIFTOUT, not SEROUT. It is probably a microwire or SPI interface.

One SHIFTOUT can send several chunks of data framed by chip select...

LOW cs
   SHIFTOUT nsdata,nsclk,MSBFIRST,[noparse][[/noparse]chunk1\10, chunk2\16, chunk3\10, chunk4\4]
HIGH cs

That adds up to 40 bits. The chunks can be either variables or constants. There may be a natural way to divide it up according to the control, address , data and don't-care bits that the device requires. What device is it?

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Tracy Allen
www.emesystems.com

PanchoFrank

Thanks Tracy and the group. I'm trying to program a National LMX2325 PLL chip used in a commercial frequency synthesizer product. The National chip has a three pin Microwire interface using CLOCK, DATA and LE (Load Enable) signals. I only need to run the synthesizer on one frequency and have determined the sequence of ones and zeros, but I'm not sure how to shift them out as one long word.

Tracy Allen

I took a quick look at it, and it seems to me that it wants two 19 bit packets. One consists of 3 don't care bits, a prescaler bit, 14 divider bits and finally control bit=1. The second consists of two divide ratios and control bit =0.
LOW LE
SHIFTOUT nsdata,nsclk, MSBFIRST, [noparse][[/noparse]%000\3, prescaler\1, refDivRatio\14, %1\1]
HIGH LE
LOW LE
SHIFTOUT nsdata,nsclk, MSBFIRST, [noparse][[/noparse]progDivRatio\11, swallowDivRatio\7, %0\1]
HIGH LE

These things can be tricky, and it takes several tries and reading between the lines.

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Tracy Allen
www.emesystems.com

PanchoFrank

Thanks Tracy. Between your info and PJ Allen's spoon feed approach, there's enough here to get me started.
PanchoFrank