16F1827 table not behaving as expected

[J. Mark Wolf]

I have a table populated with 254 word-size dwell parameters.

My 16F1827 is generating the proper range of vectors (0 - 254) to get into the table, but it's coming back with nonsense.

Screen capture below:

The left portion of the screen is my table with Serout2 commands to report the two variables inquestion, Measurement and DacDwell, immediately upon exiting the table.

The right portion of the screen capture shows the printout from the two Serout2 commands.

As you can see, the DacDwell parameter slams between $0000 and $061b, when varying the vector variable just slightly.

I'm assuming that a byte variable is adequate for vectoring into the table, since there are only 253 "items". Do I have this correct? In fact changing Measurement to a word variable had no effect.

I know it's probably something stupid I'm doing, but can anyone spot the problem?

[Darrel Taylor]

Well, the table has 254 elements, so it goes from 0 - 253.
When the value is 254 it doesn't change the output variable.

But you woud think the other numbers should have a value...

Can you post the table so I don't have to retype it?
I'll take a look tomorrow.

[Bruce]

For LOOKUP2 your table is limited to 85 list items unless you're using an 18F part..

[J. Mark Wolf]

For LOOKUP2 your table is limited to 85 list items unless you're using an 18F part..

Hi Bruce

The compiler was not balking at the table size, and I confirmed with Darrel that the table size limit has been expanded, and that the manual has not yet been updated to reflect this.

[Bruce]

Hi Mark,

You can run a simple test to see what the limit is with the table attached.

Setup a loop to call your LOOKUP2 routine with an index value from 0 to 99.

Where does it fail?

[Darrel Taylor]

Hi J.,

When you asked about LOOKUP2 previously, I had to ask.
The answer I got was 256.

That was only half right.
The compiler executable was changed ... but the macro's were not.
So while the compiler won't complain up to 256 ... the macros only work up to 85. (256/3)

Charles says the executable will be changed back to 85.
I think the macros should be changed to work with 256, but I'd have to do it in that case.
Unless Bruce beats me to it.

Are those EXT tables looking better yet?

[J. Mark Wolf]

Hi Mark,

You can run a simple test to see what the limit is with the table attached.

Setup a loop to call your LOOKUP2 routine with an index value from 0 to 99.

Where does it fail?

Hi Bruce

I thought the same thing driving home from work.

I tried it and it does indeed go "off in the weeds" after reading 85 elements.

So I take it that mere mortals cannot tweak the macros?

I can decimate my table to remove the leading zero "placekeepers" and redundant upper section to get below 85 elements, but then I'll have to play some other games to assert some artificial offsets to enter the table correctly under differing circumstances.

This is a case where the compiler/macros really should be tweaked to allow larger tables, to allow things like thermistor tables, etc.

Maybe small table limits made sense back when the devices had little code space, but that's not as true anymore.

[J. Mark Wolf]

Well, the table has 254 elements, so it goes from 0 - 253.
When the value is 254 it doesn't change the output variable.

But you woud think the other numbers should have a value...

Can you post the table so I don't have to retype it?
I'll take a look tomorrow.

Hi Darrel

You're correct, I mispoke, 254 items in the table.

Thanks for looking.

Table below:

'
'************************************************* ******************************
'
' The table below forms the basis for a variable frequency amplitude modulator, the envelope for which is
' generated from the 16F1827 on-board DAC and table below.
'
' This table contains the values for the dwell time between each DAC point
' of the envelope. It corresponds to A2D measurement (counts / 4) of the
' 5volt analog signal.
'
' Measurement = A2D counts / 4 (full range becomes 0 - 255)
'
' DacDwell = microseconds between DAC points
'
'************************************************* ******************************
'
DwellTable:
'
lookup2 Measurement,[$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '0 - 7
$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '8 - 15
$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '16 - 23_
$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '24 - 31
$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '32 - 39
$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '40 - 47
$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '48 - 55
$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '56 - 63
$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '64 - 71
$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '72 - 79
$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '80 - 87
$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '88 - 95
$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '96 - 103
$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '104 - 111
$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '112 - 119
$0000,$0000,$0000,$0000,$0000,$0000,$0000,$0000,_ '120 - 127
$5161,$4c48,$47ce,$43d1,$403f,$3d09,$3a21,$377d,_ '128 - 135 1.5pps - 2.2pps
$3513,$32dd,$30d4,$2ef3,$2d36,$2b99,$2a18,$28b1,_ '136 - 143 2.3pps - 3.0pps
$2761,$2626,$24fe,$23e7,$22e1,$21e9,$20fe,$2020,_ '144 - 151 3.1pps - 3.8pps
$1f4d,$1e85,$1dc6,$1d10,$1c63,$1bbe,$1b20,$1a89,_ '152 - 159 3.9pps - 4.6pps
$19f9,$196e,$18ea,$186a,$17ef,$177a,$1708,$169b,_ '160 - 167 4.7pps - 5.4pps
$1632,$15cc,$156a,$150c,$14b1,$1458,$1403,$13b0,_ '168 - 175 5.5pps - 6.2pps
$1360,$1313,$12c8,$127f,$1238,$11f4,$11b1,$1170,_ '176 - 183 6.3pps - 7.0pps
$1131,$10f4,$10b9,$107f,$1047,$1010,$0fda,$0fa6,_ '184 - 191 7.1pps - 7.8pps
$0f74,$0f42,$0f12,$0ee3,$0000,$0000,$0000,$0000,_ '192 - 199 7.9pps - 8.2pps & 900Hz w/ no mod
$0000,$0000,$0000,$0000,$0000,$0000,$5161,$4c48,_ '200 - 207 900Hz w/no mod & 1.5pps - 1.6pps
$47ce,$43d1,$403f,$3d09,$3a21,$377d,$3513,$32dd,_ '208 - 215 1.7pps - 2.5pps
$30d4,$2ef3,$2d36,$2b99,$2a18,$28b1,$2761,$2626,_ '216 - 223 2.6pps - 3.3pps
$24fe,$23e7,$22e1,$21e9,$20fe,$2020,$1f4d,$1e85,_ '224 - 231 3.4pps - 4.1pps
$1dc6,$1d10,$1c63,$1bbe,$1b20,$1a89,$19f9,$196e,_ '232 - 239 4.2pps - 4.9pps
$18ea,$186a,$17ef,$177a,$1708,$169b,$1632,$15cc,_ '240 - 247 5.0pps - 5.7pps
$156a,$150c,$14b1,$1458,$1403,$13b0],dacdwell '248 - 253 5.8pps - 6.3pps
'
return

end