Hi all,
     I have been working on a serial routine using the USART on the 16C74.
 My question is why doesn't it work on MPSIM?

I have checked it out several times using the data sheet for 16CXX series.
 At first I can see PIR1 <4> is clear when I load the tx data, but when it
becomes set I don't get an interrupt!  Also I never see the tx pin on portc
move.  Do I have to initiate anything else for my program to work?  See
below for program and the response from MPSIM.

;*****************************************
;    serial routine for 16C74 (18/02/97)
;*****************************************

#INCLUDE <16CXX.INC>

TEMP EQU  0X10H     ;TEMP STORAGE



ORG  0X00H
GOTO MAIN


ORG  0X04H
GOTO INTERUPT



MAIN:
CLRF TEMP           ;CLEAR THE STORAGE

MOVLW     B'00000000'         ;SET PORTC AS ALL OUTPUTS
TRIS PORTC               ;    ''
CLRF PORTC               ;CLEAR THE PORT



bsf  STATUS,rp0          ;switch to bank one
BSF  INTCON,GIE          ;ENABLE INTERUPTS

     movlw     .129      ; set up baud rate  (9600 @ 20Mhz)
     movwf     spbrg          ;    ''
bsf  txsta,brgh          ; high baud
bcf  txsta,sync          ;enable port
bcf  status,rp0
bsf  rcsta,spen          ;  ''

bsf  status,rp0          ;bank1
bsf  pie1,txie      ;enable int
bcf  txsta,tx9      ;disable 9 bit
bsf  txsta,txen          ;enable transmission
bcf  status,rp0          ;bank0

MOVFW     TEMP           ;GET TEMP VALUE INTO W
MOVWF     TXREG               ;SEND TO THE TRANSMIT REG



ENDLESS_LOOP:
     NOP
     GOTO ENDLESS_LOOP




INTERUPT:
INCF TEMP,F
MOVFW     TEMP           ;data to be transmitted
movwf     txreg               ;transmit
RETFIE                   ;RETURN




Here is the response I get from MPSIM:



SERIAL           RADIX=X   MPSIM 5.00 D    16c74   TIME=671502.00u
223945?=Help
 ----------------------------------------------------------------------------
 ----
PORTC: 00000000  TXREG: 00000000  TRISC: 00000000  TXSTA: 00100100
PIR1: 00010000  PIE1: 00010000  RCSTA: 10000000  SPBRG: 10000001  PORTA:
0001000
PORTB: 11111111  PORTD: 11111111  PORTE: 00000000  W: 00000000  TEMP:
00000000
INTCON: 10000000

 ----------------------------------------------------------------------------
 ----
Interrupt at address 16
0017 2816       GOTO    ENDLESS_LOOP
% LO C:\PICDE\HNC\SERIAL
Hex Code loaded
Listing File Loaded
Symbol table loaded
277488 bytes memory free
% RS
Processor Reset
% GO
Interrupt at address 18
0019 2818       GOTO    ENDLESS_LOOP
% AD INTCON,B,8
% C
Interrupt at address 18
0019 2818       GOTO    ENDLESS_LOOP
%



Many thanks for any input (good or bad),
Brian.