Convert a two-byte BCD into a single byte

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;#             (C) Copyright 1997 by Vault Information Services              #
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;********************************************************************
;********************************************************************
;** Function: bcd_to_byte                                          **
;** Purpose:  Convert a two-byte BCD into a single byte            **
;** Input:    A    = Hi byte to convert (ASCII 0x30-0x39,0x41-0x46)**
;**           R0   = Lo byte to convert (ASCII 0x30-0x39,0x41-0x46)**
;** Output:   A    = Converted value (binary 0x00-0xFF)            **
;** Destroyed Registers: None                                      **
;********************************************************************
;********************************************************************
bcd_to_byte:
    XCH     A,R0
    SUBB    A,#30h
    JNB     ACC.4,bcd_to_byte_2
    SUBB    A,#07h
bcd_to_byte_2:
    XCH     A,R0
    SUBB    A,#30h
    JNB     ACC.4,bcd_to_byte_3
    SUBB    A,#07h
bcd_to_byte_3:
    SWAP    A
    ORL     A,R0
    RET