MSSP with 16F876A

I feel completely retarded not being able to figure out what went wrong. Here's the code, it's just meant to send a repeating pulse out of SDO by using the MSSP module in Master mode.


The first few lines make sure that all the ports on the device are digital (Lest I want to expand the code to somehow use PortA). I use the bit setting to set up the direction of the serial pins to what the datasheet says to use (Clear bit 5 and 3, set 4), and I set the SPI enable bit in SSPCON. (Switch back to Bank 0)

I check the SSPSTAT<BF> bit to check if the serial shift register is done outputting, goes back to wait for it if it's not ready, or puts 0x66 in to send if it is done. As far as the datasheet says, as soon as there is data in the SSPBUF, it's supposed to shift it out, but it just sits there with the pins high. I must've made an obvious mistake that someone can point out, right?

Don't you have to send something before you can get a buffer full condition and once you get BF then you need to read it to prevent a collision.

Mike.

If I'm looking at it and it's 0 because the buffer is empty, it should work fine with the condition.

ArtemisGoldfish said:

If I'm looking at it and it's 0 because the buffer is empty, it should work fine with the condition.

Click to expand...

Won't it wait forever?

Mike.

Hahah, now that you mention it, I maybe should've used BTFSC. I also noticed that I was trying to read from SSPSTAT in the wrong bank. I'll fix these and see what happens.

ArtemisGoldfish said:

Hahah, now that you mention it, I maybe should've used BTFSC. I also noticed that I was trying to read from SSPSTAT in the wrong bank. I'll fix these and see what happens.

Click to expand...

I don't think that will cure the problem. Try writing to SSPBUF, then wait for BF, then read SSPBUF, then loop.

Mike.

This time I use the cond routine to go into Bank 1, copy the SSPSTAT register to W, go back to Bank 0, and put W into a general purpose register. I BTFSC the BF bit to see if it's not set, if it's all fine, it goes and writes into SSBUF. In the simulator I'm using, it actually gets to writing 0x66 to SSPBUF, but for some reason, the simulator doesn't/can't properly execute the BSF SSPCON,5 instruction. (Using Oshonsoft's PIC Simulator) In the space where it usually says the instruction, when I step through, the BSF SSPCON,5 instruction just appears as "BSF". Could just be a problem with the simulator now, I'll have to test the program on the real hardware when I get my ICD2.