Thanks. I am reposting the source code here again.

Initialisation...
			CLR	TR1				;Stop Timer1 for Serial Baudrate
			MOV	TMOD,#21h			;Timer 1 is 8 bit with auto-reload
			MOV	TH1,#Baudrate		;Load serial port 0 & 1 baudrate to timer1 (for serial 0 & 1)
			MOV	PCON,#80h			;Serial 0 SMOD=1 where Serial Port 0 baud rate is doubled								
			MOV	SCON0,#50h			;Serial 0 in Asynchronous 10 bits, Receiver Enable (Mode 1)
			MOV	WDCON,#80h			;Serial 1 SMOD=1 where Serial Port 1 baud rate is doubled								
			MOV	SCON1,#50h			;Serial 1 in Asynchronous 10 bits, Receiver Enable (Mode 1)
			MOV	IE,#50h			;Enable serial port 0 & 1 interupt only
			MOV	IP,#10h			;Set serial port 0 interupt highest priority
			SETB	TR1				;Start Serial Port timer 1
			CLR	NRTS0				;Enable receiving data from serial port 0 
			CLR	NRTS1				;Enable receiving data from serial port 1 
			SETB	EA				;Start/Enable interupt input


The MODBUSCRC routines calculate the CRC value and send the bytes to the transducer.
The CRC calculation is correct.

;******************************************************************************************
;	Subroutines	- SModbusCRC
;	Input : 	TSlaveAdd,TFunctionCode,TData1-TData20,TCRCn,TCRCi,TCRCj,TCRCDi
;	Output : 	TCRCMSB,TCRCLSB
;******************************************************************************************
SModbusCRC:		MOV	TCRCMSB,#0FFh	;(1)
			MOV	TCRCLSB,#0FFh	
			MOV	TCRCi,#0		;(2)
			MOV	TCRCDi,TSlaveAdd
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
Goto3:		MOV	TCRCj,#0		;(3)
			MOV	A,TCRCLSB
			XRL	A,TCRCDi		;(4)
			MOV	TCRCLSB,A
Goto5:		INC	TCRCj			;(5)
			CLR	C
			MOV	A,TCRCMSB		;(6)
			RRC	A
			JC	MSBCarry
			MOV	TCRCMSB,A
			MOV	A,TCRCLSB
			SJMP	RRCLSB
MSBCarry:		MOV	TCRCMSB,A
			MOV	A,TCRCLSB
			SETB	C
RRCLSB:		RRC	A
			JC	LSBCarry
			MOV	TCRCLSB,A		;(6)
			SJMP	Goto8
LSBCarry:		MOV	TCRCLSB,A		;(6)
			MOV	A,TCRCMSB		;(7)
			XRL	A,#0A0h
			MOV	TCRCMSB,A
			MOV	A,TCRCLSB
			XRL	A,#001h
			MOV	TCRCLSB,A
Goto8:		MOV	A,TCRCj		;(8)
			CJNE	A,#08,Goto5
			INC	TCRCi			;(9)
			MOV	A,TCRCi		;(10)
			CJNE	A,TCRCn,ReloadData
			MOV	A,TCRCLSB		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			MOV	A,TCRCMSB		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			MOV	Counter,#0
			RET				;(11)	

ReloadData:		CJNE	A,#1,ReloadData1
			MOV	TCRCDi,TFunctionCode
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData1:	CJNE	A,#2,ReloadData2
			MOV	TCRCDi,TData1
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData2:	CJNE	A,#3,ReloadData3
			MOV	TCRCDi,TData2
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData3:	CJNE	A,#4,ReloadData4
			MOV	TCRCDi,TData3
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData4:	CJNE	A,#5,ReloadData5
			MOV	TCRCDi,TData4
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData5:	CJNE	A,#6,ReloadData6
			MOV	TCRCDi,TData5
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData6:	CJNE	A,#7,ReloadData7
			MOV	TCRCDi,TData6
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData7:	CJNE	A,#8,ReloadData8
			MOV	TCRCDi,TData7
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData8:	CJNE	A,#9,ReloadData9
			MOV	TCRCDi,TData8
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData9:	CJNE	A,#10,ReloadData10
			MOV	TCRCDi,TData9
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData10:	CJNE	A,#11,ReloadData11
			MOV	TCRCDi,TData10
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData11:	CJNE	A,#12,ReloadData12
			MOV	TCRCDi,TData11
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData12:	CJNE	A,#13,ReloadData13
			MOV	TCRCDi,TData12
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData13:	CJNE	A,#14,ReloadData14
			MOV	TCRCDi,TData13
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData14:	CJNE	A,#15,ReloadData15
			MOV	TCRCDi,TData14
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData15:	CJNE	A,#16,ReloadData16
			MOV	TCRCDi,TData15
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData16:	CJNE	A,#17,ReloadData17
			MOV	TCRCDi,TData16
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData17:	CJNE	A,#18,ReloadData18
			MOV	TCRCDi,TData17
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData18:	CJNE	A,#19,ReloadData19
			MOV	TCRCDi,TData18
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData19:	CJNE	A,#20,ReloadData20
			MOV	TCRCDi,TData19
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData20:	CJNE	A,#21,ReloadData21
			MOV	TCRCDi,TData20
			MOV	A,TCRCDi		;** Send Serial to Transducer **
			CALL	SSerialToTrans	;** Send Serial to Transducer **
			JMP	Goto3
ReloadData21:	JMP	Goto3

;******************************************************************************************
;	Subroutines	- SSerialToTrans
;	Send the serial value to Transducer
;	Input:	A	
;******************************************************************************************
SSerialToTrans:	MOV	ModbusData,A		;Copy value received from SPI and send to PC
			CALL	SModbusOut
			RET


;******************************************************************************************
;	Subroutines	- SModbusOut
;	Input : 	ModbusData
;******************************************************************************************
SModbusOut:		CLR	EA				;disable interupt input from all
			SETB	NRTS0				;Not prepare to receive Serial signal
			SETB	NRTS1				;Not prepare to receive Serial signal
			;CALL	SSerialDelay		;Delay 600us to ensure no on going serial transmission
			MOV	A,ModbusData		;send data in hex value

			;JB	NCTS1,$			;Wait until PC ready to receive serial signal
			CLR	TI_1				;Clear send complete flag
			MOV	SBUF1,A			;Send to PC
			JNB	TI_1,$			;Wait until send complete
			CLR	TI_1				;CRITICAL ( DO CLEAR AFTER SEND OR FOREVER LOOP )
			RET