DECLARE HSERIAL_BAUD = 9600 ' Set baud rate to 9600
DECLARE HSERIAL_RCSTA = %10010000 ' Enable serial port and continuous receive
DECLARE HSERIAL_TXSTA = %00100100 ' Enable transmit and asynchronous mode
DECLARE HSERIAL_CLEAR = ON ' Enable Error clearing on received characters
The 16F84 is a far inferior chip (and costs a lot more!), unless the 628 program is only using the chip as an 84 you won't be able to replace it with an 84.
In particular the 628 has three more I/O pins, an internal oscillator, internal comparators, a USART, twice the program memory, more GPR's.
As long as none of those are used it willbe simple to replace with an 84.