Migrating to 18F4420

I have a project that threatens to outgrow a 16F877A and so have upgraded to the 16F4420. This is quite a step for me as, I have not done much work with a 40 pin chip prior - and never anything with the 18F. So... I've stripped the board down to the MCU, a 4x20 LCD, an I2C clock (3231 module), and required supporting circuitry.

Using meCONFIG, I have managed to configure the chip and, the heartbeat LED is blinking merrily; the LCD starts up and displays exactly like the old '877, but the I2C clock is stubborn. I'm wondering if there is anything in the CONFIG causing the problem, or if perhaps there is some difference in the syntax that I have not seen?

Any help will be appreciated!

Configuration:

Code:

__config _CONFIG1H, _OSC_HSPLL_1H & _FCMEN_OFF_1H & _IESO_OFF_1H __config _CONFIG2L, _PWRT_OFF_2L & _BOREN_SBORDIS_2L & _BORV_3_2L __config _CONFIG2H, _WDT_OFF_2H & _WDTPS_512_2H __config _CONFIG3H, _CCP2MX_PORTC_3H & _PBADEN_OFF_3H & _LPT1OSC_OFF_3H & _MCLRE_ON_3H __config _CONFIG4L, _STVREN_ON_4L & _LVP_OFF_4L & _XINST_OFF_4L & _DEBUG_OFF_4L __config _CONFIG5L, _CP0_OFF_5L & _CP1_OFF_5L __config _CONFIG5H, _CPB_OFF_5H & _CPD_OFF_5H __config _CONFIG6L, _WRT0_OFF_6L & _WRT1_OFF_6L __config _CONFIG6H, _WRTC_OFF_6H & _WRTB_OFF_6H & _WRTD_OFF_6H __config _CONFIG7L, _EBTR0_OFF_7L & _EBTR1_OFF_7L __config _CONFIG7H, _EBTRB_OFF_7H

CODE:

Code:

'-----DEFINES------------------------------------------------------------------ '-----OSC DEFINE OSC 4 '----ADC DEFINE ADC_BITS 10 ' Set number of bits in result 'DEFINE ADC_CLOCK 3 ' Set clock source (rc = 3) DEFINE ADC_SAMPLEUS 100 '-----LCD DEFINE LCD_DREG PORTD DEFINE LCD_DBIT 4 DEFINE LCD_RSREG PORTD DEFINE LCD_RSBIT 3 DEFINE LCD_EREG PORTD DEFINE LCD_EBIT 2 DEFINE LCD_LINES 4 '-----REGISTERS SET------------------------------------------------------------ CMCON = %00000111 'DISABLE COMPARITOR TRISA = %00011111 ' Set PORTA.OUTPUT; ADC TRISB = %00000000 ' Set PORTB OUTPUT TRISC = %00000000 ' Set PORTC TRISD = %00000000 ' Set PORTD OUTPUT TRISE = %00000000 ADCON0 = %10100001 ADCON1 = %10000010 ' RIGHT justify; Set AN0 - AN5 ADC '-----LED LINE1 CON $80 LINE2 CON $C0 LINE3 CON $94 LINE4 CON $D4 '-----I2C SCL VAR PORTE.1 SDA VAR PORTE.2 'DEFINE I2C_SLOW 1 'DEFINE I2C_HOLD 1 'DEFINE I2C_SCLOUT 1 '-----INDICATOR LIGHTS LIT_ADD CON %01110010 '-----GAUGES REG_CHP1 CON %01011000 REG_CHP2 CON %01011010 GAGE VAR BYTE '-----CLOCK/ CALENDAR REG_VAL VAR Byte[12] RTC_ADD CON %11010000 REG_TIM CON $00 REG_CTL CON $07 REG_STS CON $0F CURR_MIN VAR WORD OLD_MIN VAR byte OLD_DAY VAR BYTE '-----INITIALIZE--------------------------------------------------------------- '----SET TIME 'Seconds, minutes, hours, day of week, date, month, year REG_VAL[0] = 00 'SECONDS REG_VAL[1] = 12 'MINUTES REG_VAL[2] = 19 'HOURS REG_VAL[3] = 03 'DOW REG_VAL[4] = 18 'DAY REG_VAL[5] = 02 'MONTH REG_VAL[6] = 15 'YEAR REG_VAL[7] = %01100000 'SPECIAL REG_VAL[8] = %00001000 'SPECIAL REG_VAL[9] = %00001000 'SPECIAL I2CWrite SDA, SCL, REG_CTL, $0E, [REG_VAL[7]] GOSUB CLK_WRITE '-----MISC '.6 D1 VAR BYTE LP VAR BYTE ADC_VAL VAR WORD[3] IND_LIT VAR BYTE PAUSE 250 LCDOUT $FE, $01 ' Bit 7 = LCDOUT $FE, LINE1,"--STEGETROLLER--" PAUSE 250 LCDOUT $FE, LINE2,"---START-UP" PAUSE 1250 LCDOUT $FE, $01 MAIN: FOR LP = 1 TO 3 ADCIN LP, ADC_VAL[LP] PAUSE 10 NEXT LP 'I2CWrite SDA, SCL, LIT_ADD, $00, [IND_LIT] 'IND_LIT = IND_LIT + 1 'I2CWrite SDA, SCL, REG_CHP1, $00, [GAGE, GAGE] 'GUAGE 1 - TEMP 'pause 100 'GAGE = GAGE + 10 PORTA.5 = 1 PAUSE 100 PORTA.5 = 0 PAUSE 100 GOSUB CLK_READ GOSUB UPDATE_DISPLAY GOTO MAIN UPDATE_DISPLAY: 'LINE1 LCDOUT $FE, LINE1, DEC1 REG_VAL[3], "<", DEC2 REG_VAL[5], "/", DEC2 REG_VAL[4] LCDOUT $FE, LINE1 + 14, "[", DEC4 CURR_MIN, "]" LCDOUT $FE, LINE2, DEC4 ADC_VAL[1], ":", DEC4 ADC_VAL[2], ":", DEC4 ADC_VAL[3] LCDOUT $FE, LINE3, DEC2 REG_VAL[2], ":", DEC2 REG_VAL[1], ":", DEC2 REG_VAL[0] LCDOUT $FE, LINE4, BIN16 ADC_VAL[1] '-----READ CLOCK AND CONVERT TO DECIMAL CLK_READ: I2CRead SDA, SCL, RTC_ADD, $00, [REG_VAL[0], REG_VAL[1], REG_VAL[2], REG_VAL[3], REG_VAL[4], REG_VAL[5], REG_VAL[6], REG_VAL[7], REG_VAL[8], REG_VAL[9], REG_VAL[10], REG_VAL[11], REG_VAL[12]] FOR LP = 0 TO 6 D1 = REG_VAL[LP] D1 = D1 & $70 D1 = D1 >> 4 D1 = D1 * 10 REG_VAL[LP] = D1 + (REG_VAL[LP] & $0F) NEXT LP CURR_MIN = REG_VAL[2] * 60 + REG_VAL[1] Return '-----CONVERT TO BCD VALUES, WRITE TO CLOCK REGISTERS CLK_WRITE: FOR LP = 0 TO 6 D1 = REG_VAL[LP] DIG 1 D1 = d1 << 4 D1 = D1 + (REG_VAL[LP] DIG 0) REG_VAL[LP] = D1 NEXT LP I2CWrite SDA, SCL, RTC_ADD, $00, [REG_VAL[0], REG_VAL[1], REG_VAL[2], REG_VAL[3], REG_VAL[4], REG_VAL[5], REG_VAL[6], REG_VAL[7]] GOSUB CLK_READ Return

The code is quite messy as I've been up way too late trying to solve the issue myself and now, as I prepare for work, am admitting defeat. Still, it does work on the 877, just wondering what the problem on the 4420 might be?