PIC programmers for the parallel port

Using a simple PIC programmer at the parallel port can cause headaches under certain Windows versions. First of all, you must select one of the port access drivers, because the Windows API (application interface) doesn't have suitable functions for the parallel port. Even worse: Sometimes the printer driver (or whatever?) accesses the port though WinPic tries to occupy the port itself. This somehow depends on the signal used to read back the data from the PIC. Especially the PAPER OUT signal seems to attact Window's attention .. and should be avoided for this reason. I did not check if removing all printer drivers can help, if you know more please let me know.

WARNING ! Because Windows sometimes fools around with the parallel port, and we don't know the state of the parallel port before starting the programmer, first connect the programmer with the PC, then turn the PC on, start the programmer, and insert the PIC into the socket (or connect the ICSP cable) shortly before programming ! If you get an error message from WinPic saying "Windows fooled around with the parallel port bits", read this .

However, it may be possible to use a few -in the days of DOS widely used- interfaces. Supported (but not all tested) are the following interfaces, along with their major differences.

**PIC programmers for the parallel port**
Interface type	Data PC->PIC	Clock PC->PIC	Data PIC->PC	Vpp Control	Vdd Control	Remarks
PIC FLASH programmer V1 (SM6LKM, 2002-10-01)	D2, not inverted	D3, not inverted	ACK, inverted	D4, inverted (L=Vpp on)	D0, not inv. (H= Vdd on)	ICSP adapter with D7 = ICSP disconn(*)
PIP84 (by SM6LKM)	D2, not inverted	D3, not inverted	PAPER,inverted	D4, inverted (L=Vpp on)	D0, inverted (L= Vdd on)	D1=green LED D7=ICSP disconnect
PIP84 (alternative)	D2, not inverted	D3, not inverted	ACK,inverted	D4,inverted	D0,inverted	D1=green LED D7=ICSP disconnect
Tait, 7406, 4066	D0, inverted	D1, inverted	ACK, inverted	D3, inverted	D2, inverted	7406=inverter 4066=switches
Tait, 7407, 4066	D0, not inverted	D1, not inverted	ACK, not inverted	D3, not inverted	D2, not inverted	7407=non- inverting driver
Tait, 7406, PNP	D0, inverted	D1, inverted	ACK, inverted	D3, not inverted	D2, not inverted	7406=inverter, + PNP-transistor
Tait, 7407, PNP	D0, not inverted	D1, not inverted	ACK, not inverted	D3, inverted	D2, inverted	David Tait's "classic" design
Microchip "AN 589"	D0	D1	ACK	D3	none (always on)	D2=data tristate, D5=clock tristate, D4=Pull MCLR down

**Signals on the PC's 25-pin "LPT" connector (SUB-D)**
Pin Nr	Signal	token name in interface definition file	Direction	Description (usual function)
1	/STROBE	str	PC->printer	'Byte clock'
2	D0	D0	PC->printer	Centronics Data
3	D1	D1	PC->printer	Centronics Data
4...8	...	...	PC->printer	Centronics Data
9	D7	D7	PC->printer	Centronics Data
10	/ACK	ack	printer->PC	Acknowledge
11	BUSY	bsy	printer->PC	Busy or Error
12	PAPER	pap	printer->PC	high=printer ran out of paper
13	SELECTED	sld	printer->PC	high=printer is on-line
14	/ALF	alf	PC->printer	automatic line feed
15	/ERROR	err	printer->PC	out of paper, error, offline
16	/INIT	ini	PC->printer	resets the printer
17	/PRINTER SEL	psl	PC->printer	low = select printer
18..25	GROUND		-	connect ALL LINES to ground

Not listed in the above table: ICSP Connect/Disconnect ... based on an idea by Johan Bodin:: Centronics D7 (inverted) is used as an additional control line for in-circuit programming. This signal is used to *totally* disconnect the programmer from the target system (using relay(s) and/or CMOS analog switches or whatever). This eliminates the need to plug/unplug the programming connector for code test runs. Some target systems may have very hi-z circuits connected to the programming pins, RB6/RB7 (GP0/GP1).
D7 = LOW means "Programmer shall be connected to target"
D7 = HIGH means "Programmer shall be disconnected from target" (you'll find D7 HIGH after booting the PC in many cases, so HIGH=DISCONNECT is the safer state)
After switching this signal to LOW (=connect programmer to target), the software waits at least 200 milliseconds until the first attempt to switch the PIC into programming mode. This should be enough for electromagnetic relays.

Parallel port trouble

Sometimes (especially under Windows XP) you may get a sloppy error message from WinPic telling you that "Windows fooled around with the parallel port". The reason for this may be a scanner driver, printer driver, or the plug-and-play hardware detection which permanently polls the port for new devices. Of course, this will spoil the operation of a PIC programmer connected to the parallel port !

The problem could sometimes be fixed by adding (or modifying) the following key in the windows registry :

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Parport\Parameters]

"DisableWarmPoll"=dword:00000001

Search the web for "Jan's Parallel Port FAQ"; the site contains details about this registry hack.
Caution: Only modify the registry if you know what you're doing ;-)

Original Author for WinPic: Wolfgang Buescher (DL4YHF)
Adapted to WxPic by Philippe Chevrie