This is an 877 and not an 877A, correct? As Wouter suggests, you need to get !MCLR up to Vihh in a hurry after Vdd is applied, although with a crystal, "in a hurry" is quite a long time. But if it's an A, you may also need to be sure RB3 is pulled low. The data sheet says that Vihh only needs to be 3.5 volts over Vdd, but back a while ago, a lot of folks went to great pains to ensure that Vihh was OVER 12 volts. I haven't proven a need for that, but it would be worthwhile to check for 12.1 volts or so at Vihh. I think earlier you indicated that you had good evidence that your program was still running, but in the current note, you talk as if perhaps data isn't making it into RB6/7. Notice that it is the reset that sets the pins to input, and not programming mode. If you didn't go from reset to programming mode without going through run mode, then you may be in programming mode, but unable to drive data into RB6/7 because one or both was set to be an output by the program. But, if you can see your program changing your LCD, then you aren't in programming mode and you should be looking at the value of Vihh. 72/73 de WB8RCR http://www.qsl.net/wb8rcr didileydadidah QRP-L #1446 Code Warriors #35 ----- Original Message ----- From: "Daren X" <> To: Sent: Monday, January 05, 2004 6:37 AM Subject: [PIC:] VIHH on MCLR doesnt put PIC in programming mode > Hi Everyone, > After doing more testing on my ICSP circuit I strongly believe that the > PIC isn't going into programming mode once VIHH is applied to MCLR. It > simply goes along and executes code as normal. Has anyone seen similar > behaviour? > > The pic (16f877) has a max232 connected to its Tx and Rx lines, is > running a 20MHz crystal with 2 15pf caps. > > It also has a 4x20 LCD screen connected to RD1-7, in 4 bit mode. > > Regards, > Daren > > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listserv@mitvma.mit.edu with SET PICList DIGEST in the body > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listserv@mitvma.mit.edu with SET PICList DIGEST in the body