Hi Steve and Kai,

First, yes I have pullups on port 0. As for the code, I am pasting it below, with some strategic redactions. If it loses its formatting, someone tell me the command to prevent that and I'll try again.

Thanks,
Joe


$TITLE(*****)

; This program is to test the *****
; circuit via the µ-controller circuit.

CSEG AT 0
JMP START

START:

; Define control lines specific to this project

SBIT TE = P3.2 ; T**** E**** (active high)
SBIT MANW = P3.3 ; Manual Write, (active low)
SBIT MR = P3.4 ; Master Reset *****, (actve low)
SBIT CS = P3.5 ; **** Chip Select, (active low)
SBIT ****S = P3.6 ; **** Select, (~*****/*****)

; Set UART Mode and BAUD rate

MOV SCON, #0x50 ; Mode 1, 8-bit UART, enable receiver
MOV TMOD, #0x20 ; Timer 1, mode 2, 8-bit reload
MOV TH1, #0xFD ; TH1 = 253, 9600 baud w/11.0592 MHz xtal
SETB TR1 ; Turn on Timer 1
MOV SBUF, #'.' ; Send ACK to host
JNB TI, $ ; Wait for send
CLR TI ; Reset flag

; Initialize µ-controller control lines

CLR TE ; Put TE low, in-active state
SETB MANW ; Put MANW hi, in-active state
SETB MR ; Put MR hi, in-active state
SETB CS ; Put CS hi, in-active state
CLR ****S ; Put ****S low, select *****

; Body of program. Structure is a single pass loop. Program
; operation will normally idle at the instruction labeled LOOP.

LOOP: JNB RI, $ ; Wait for host command
CLR RI ; Command received, clear flag
MOV A, SBUF ; Move command to Accumulator
CJNE A, #'L', RUN ; If not (L)oad, test (R)un

; Reset *****
CLR TE ; Put TE low, in-active state
SETB MANW ; Put MANW hi, in-active state
; These are necessary for MR to
; be effective.
CLR MR ; Before loading new data, SETB MR ; clear the old one.

LOAD: MOV SBUF, A ; Echo 'L' command
JNB TI, $ ; Wait for send
CLR TI ; Send complete, reset flag
MOV SBUF, #'.' ; Confirm command accepted
JNB TI, $ ; Wait for send
CLR TI ; Send complete, clear flag
JNB RI, $ ; Wait for next data byte
CLR RI ; Data received, clear flag
MOV A, SBUF ; Move data byte into accumulator
CJNE A, #'.', L2 ; Test for end of data
MOV SBUF, #'x' ; Acknowledge end of data
JNB TI, $ ; Wait for send
CLR TI ; Send complete, reset flag
MOV P0, #0xFF ; Set port to hi states
JMP LOOP ; If end of data, return
L2: MOV P0, A ; Write data byte to Port 0
CLR MANW ; Clock into *****
SETB MANW ; Reset MANW to non-active state
JMP LOAD ; Go get next data byte

RUN: CJNE A, #'R', STOP ; If not (R)un, test (S)top
MOV SBUF, A ; Echo 'R' command
JNB TI, $ ; Wait for send
CLR TI ; Send complete, reset flag
MOV SBUF, #'.' ; Confirm command accepted
JNB TI, $ ; Wait for send
CLR TI ; Send complete, clear flag
CLR CS ; Enable ****
SETB TE ; Turn on ******
JMP LOOP ; Return to main loop

STOP: CJNE A, #'S', GAIN ; Ifnot (S)top, test (G)ain
MOV SBUF, A ; Echo 'S' command
JNB TI, $ ; Wait for send
CLR TI ; Send complete, reset flag
MOV SBUF, #'.' ; Confirm command accepted
JNB TI, $ ; Wait for send
CLR TI ; Send complete, clear flag
CLR TE ; Turn off ******
SETB CS ; Disable ****
JMP LOOP ; Return to main loop

GAIN: CJNE A, #'G', OUT ; If not (G)ain, go to (O)ut
MOV SBUF, A ; Echo 'G' command
JNB TI, $ ; Wait for send
CLR TI ; Send complete, reset flag
MOV SBUF, #'.' ; Confirm command accepted
JNB TI, $ ; Wait for send
CLR TI ; Send complete, clear flag
CLR TE ; Turn off ******
SETB CS ; Disable ****
G2: JNB RI, $ ; Wait for gain setpoint byte
CLR RI ; Byte received, clear flag
MOV P0, SBUF ; Put gain byte on Port 0
MOV SBUF, #'.' ; Confirm Data set
JNB TI, $ ; Wait for send
CLR TI ; Send complete, reset flag
SETB ****S ; Select *****
CLR CS ; Select **** for input
CLR MANW ; Clock gain setpoint into *****
SETB MANW ; Return MANW to in-active state
SETB CS ; Return **** CS to in-active CLR ****S ; Select ***** again
MOV P0, #0xFF ; Reset the data bus
JMP LOOP ; Return to main loop

OUT: MOV SBUF, A ; Echo unknown command
JNB TI, $ ; Wait for send
CLR TI ; Send complete, clear flag
MOV SBUF, #'x' ; Confirm command unrecognized
JNB TI, $ ; Wait for send
CLR TI ; Send complete, reset flag
JMP LOOP ; Go back to beginning of program

END