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PICList Thread
'[PIC]: Problem with 17C766'
2000\07\18@165711 by Dave Roberts


Anyone with experience of 17C7xx serial programming ?

I'm going in circles.

Can't get the beastie to program. I noticed several mistakes in the PIC pogramming datasheet. I emailed Microchip, they have not responded.

Given the number of errors, I lack confidence in the spec. As I can' find any mistake in what I am doing, I'm at a dead end.

Here is the text of the email to microchip.


I wonder if you can help me.

I'm trying to serial program ( in circuit ) the 17C766. I'm having some trouble and having noticed errors in the programming spec datasheet thought I would check whether I'm doing something wrong or whether the datasheet is in error.

Programing Datasheet DS30274B dated 1998
Main Device Datasheet DS30289A dated 1998
Example Target Device PIC17C766/CL batch data 9922HAL ES USA

When I try to raise the voltage on TEST to 13 V ( Vihh ) it consumes excessive current ( current limit applied, 120 mA at 7V 200 mA at 10 V ).
Is the programming algorithm in the datasheet correct ? Given the number of typos I thought I would ask. I see no later version on the website.

Typos noticed :

PS10 specified as 100 usec in section 7.0 and 100 msec in two places in Figure 4.8 ( also main 17C7XX datasheet also says msec not usec in D114 on page 244 ) but 100 usec in figure 3.3 and section 6.0 table ( P9 )
End Programming command specified in Table 4.2 but no description of use anywhere - implied that sending any command ( including this ?) stops programming cycle

Figure 4.8 shows that device clock should be on RA0 whereas all other references are to RA1

Figure 4.8 states that clock should not be applied until MCLR is at Vihh yet all section 7 figues allow for it to precede Test voltage change

Table 5.2 does not state which word appears in LSbyte and which in MSbyte - see text in section 5.1

Table 5.2 shows in second word bits 0 to 5 as PM2, whereas the mplab inc file for the 17C766 implies just bit 7 ( and checksum calculations also imply just bit 7 in the mask values applied )

No power down sequence shown for serial mode ( cf figure 6.4 )

Note 1 to table in section 6.0 is wrong. It states that "VPP/MCLR pin must only be equal to or greater than VDD at times other than programming." This cannot be correct. As written, MCLR must only be at Vihh when you are not trying to program the part.

Finally, it is ambiguous in section 1.1 where it states that the clock must be able to overdrive the RC mode pulldown for the oscillator, but the clock is applied to RA1 not to OSC1 and OSC1 is not specified in Table 4.1

Any help gratefully received

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