The Signetics 2650 - The MESSUI Place

CP1002 "PIPLA" ROM
loaded). As before sp means a space,
and cr means a carriage return.
The parameter A is used to specify
the dumping format. There are three
formats allowed; you can either dump
all 8 bits of each memory byte, only the
least significant 4 bits of each, or only
the most significant 4 bits. The three
modes correspond to the following
values for parameter A:
0 -- all 8 bits dumped
1 — only the least significant 4 bits
2 — only the most significant 4 bits
If options 1 or 2 are specified, the
four bits of data are right justified and
the upper four bits are dumped as
zeroes.
The remaining command functions
provided by PIPBUG2 are virtually
identical to those of the, original
PIPBUG. Hence there is the "A" command
to examine and alter memory,
the "L" command to load from cassette
or paper tape, the "D" command to
dump to cassette or paper tape, the "S"
command to see and set the registers,
the "B" command to set a breakpoint,
the "C" command to clear a breakpoint
and the "G" command to transfer command
to a user program. These are all
used in exactly the same manner as
those of the original PIPBUG.
As with the first version of PIPBUG,
there are a number of utility subroutines
in PIPBUG2 which may be called
by user programs. The most useful
of these are described in Table 2. Note
that as mentioned earlier, some of
these sub-routines are significantly
different from those in the original
PIPBUG when it comes to use of
registers, etc.
The PIPLA line assembler starts at hex
0400. As mentioned earlier it gives no
initial identifying message and assumes
a starting origin of OCOO for the
program to be assembled. So when you
call it, the response is simply
°COO.
Apart from this, its operation is very
similar to that of the modified
assembler I described in the April 1979
issue. You can change the origin as
desired with an ORG directive, store a
string of ASCII characters with an ASCI
directive, and return to PIPBUG2 with
an END directive. The only directive
not available is the DATA directive.
There is only one other point to
remember. The input buffer used by
PIPLA is only 24 characters long, compared
with the buffer of about 60
characters used by the modified
assembler. So you cannot have a long
string in an ASCI directive, nor can you
fa in comments after the operand field
of an instruction line. But you can still
have normal comment lines (identified
by an asterisk as the first character), as
long as they are shorter than 24
characters.
TABLE 2: User-accessible subroutines In PIPBUG2
LABEL FUNCTION CALL BY
CHIN
COUT
.....
Inputs a character to RO from
the serial terminal
Outputs a character from RO to
the serial terminal
BIN Reads two hex chars from the
terminal, forms byte in R1
BOUT
Prints the byte in R1 as a two-digit hex
number (Data in RO is destroyed)
LKUP Converts a hex char in RO into
a 4-bit number (returned in RO also)
GNUM Fetches a 4-digit number from
the input buffer, stores in R1 and R2
STRT Stores R1, R2 into 80D, 80E
INCRT Increments contents of 80D, 80E
CRLF Sends CR, LF to terminal
CHNG Converts the byte in RO into two
hex chars returned in R1, R2
FORM Outputs 3 spaces to terminal
GAP Output 50 spaces to terminal
....i
...
ZBSR *0009
(BB 89)
ZBSR *0007
(BB 87)
ZBSR *000D
(BB 8D)
ZBSR *000B
(BB 8B)
ZBSR 0026
(BB 26)
ZBSR *000F
(BB 8F)
ZBSR 0021
(BB 21)
ZBSR 0017
(BB 17)
BSTA, UN 01A9
(3F 01 A9)
BSTA, UN 028D
(3F 02 8D)
BSTA,,UN 0360
(3F 03 60)
BSTA, UN 0364
(3F 03 64)
ELECTRONICS Australia, October, 1979 77
,
,