Motorola M68HC11EVB, User Manual

Page: 30 / 103

MONITOR PROGRAM
M68HC11EVB/D 3-3 3
3.2.4 Utility Subroutines
Several subroutines exist that are available for performing I/O tasks. A jump table has been set up
in ROM directly before the interrupt vectors. To use these subroutines, execute a jump to
subroutine (JSR) command to the appropriate entry in the jump table. By default, all I/O
performed with these routines are sent to the terminal port. Redirection of the I/O port is achieved
by placing the specified value (0=SCI, 1=ACIA, 2=DUARTA, 3=DUARTB) into RAM location
IODEV.
Utility subroutines available to the user are listed in Table 3-1.
Table 3-1. Utility Subroutine Jump Table
Address Routine Description
$FF7C .WARMST Go to ">" prompt point (skip BUFFALO... message).
$FF7F .BPCLR Clear breakpoint table.
$FF82 .RPRINT Display user's registers.
$FF85 .HEXBIN Convert ASCII character in A register to 4-bit binary number.
Shift binary number into SHFTREG from the right. SHFTREG
is a 2-byte (4 hexadecimal digits) buffer. If A register is not
hexadecimal, location TMP1 is incremented and SHFTREG is
unchanged.
$FF88 .BUFFAR Read 4-digit hexadecimal argument from input buffer to
SHFTREG.
$FF8B .TERMAR Read 4-digit hexadecimal argument from terminal device to
SHFTREG.
$FF8E .CHGBYT Write value (if any) from 1 to memory location
pointed to by X. (Operation also applicable to EEPROM
locations.)
$FF91 .READBU Read next character from INBUFF.
$FF94 .INCBUF Increment pointer into input buffer.
$FF97 .DECBUF Decrement pointer into input buffer.
$FF9A .WSKIP Read input buffer until non-white-space character found.
$FF9D .CHKABR Monitor input for (CTRL)X, (DELETE), or (CTRL)W requests.
$FFA0 .UPCASE If character in accumulator A is lower case alpha, convert to
upper case.