I needed a way to look inside an F88 while it was running, so as to check what was happening to certain RAM registers. So I knocked up this RAM sniffer
On a regular basis (every 2 seconds, as determined by a system tick) the F88 bitbangs its RAM contents out. The 2520 picks this data up, if set to, and shows it as 2 lines of 4 bytes, each line starting with the address. Two buttons allow you to move up and down
Could be made into something flashy, but for now it does all I need it to. Maybe someone else can use it, I found it tremendously helpful
Connections to the circuit are 4 clipped leads - 0V, 5V, clock, data.
Some 2520 routines are there for another day and aren't used here
A timing oversight - I found that a 48MHz USB PIC needs a few NOPs in the transmit routine (as offered above) to give the 2520 a chance to store incoming and get back to data pick-up
The transmit routine could also of course include FSRs and program/EEPROM locations
Generally now I have a pushbutton in the main loop or other convenient wait place to send data on demand, using the bbdata line as both button press detect and data transmit
Or the routine p2p is called to skip the button press and delay
(this example for an 8MHz 18F1320)
pic2pic btfss showram ;wait for button release bra $-2 call ms50 ;short debounce delay movlw b'00101000' ;i/p off, bbdata o/p on movwf trisa p2p movlw b'00101000' ;i/p off, bbdata o/p on movwf trisa lfsr fsr0,0x0000 d_loop movlw 0x08 movwf temp4 movf indf0,w movwf temp1 call send_d incfsz fsr0l bra d_loop movlw b'10101000' ;i/p on, bbdata o/p off movwf trisa return
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