Southwest Specialty Products 6800 Most Significant Byte of Lower Address, END of Tape Command E

A002 à	01	MOST SIGNIFICANT BYTE OF LOWER ADDRESS
A003 à	23	LEAST SIGNIFICANT BYTE OF LOWER ADDRESS
A004 à	45	MOST SIGNIFICANT BYTE OF UPPER ADDRESS
A005 à	67	LEAST SIGNIFICANT BYTE OF LOWER ADDRESS

Typing P would turn the punch on and output the specified memory data. A sample punch output is as follows:

$M A002
$A002 02	01		MSB OF LOW ADDRESS
$A003 72	00		LSB OF LOW ADDRESS
$A004 EF	01		MSB OF HIGH ADDRESS
$A005 00	20		LSB OF HIGH ADDRESS
$A006 5F
$P			TAPE PUNCH COMMAND
S11301008E1000CE12348600C6FF3FE0E3DD005DB2
S11301108090E05160F73A8201F500FFC79771D1F2
S104012000DA
$
S1	13	0100	8E1000CE12348600C6FF3FE0E3DD005D	B2
START OF	BYTE	BLOCK	DATA	CHECK
BLOCK	COUNT	STARTING		SUM
CHARACTER	(HEX)	ADDRESS

The S1 at the start of the block is used to tell the load routine that valid punch data follows. Each punch block must begin with the S1. The 1316 is the number of bytes that follow in the block. In this case two bytes are required for the starting address of the block (01 and 00), 1016 bytes are required for the data (8E 10 00 CE 12 34 86 00 C6 FF 3F E0 E3 DD 00 50) and one byte is required for the checksum (B2). The checksum is generated by adding the complement of the start of block address and the data, 8 bits at a time. At load-in time another checksum is generated by the load routine which must match with the one generated at punch time.

As the punch begins a PUNCH ON (1216) control character will be output to the punch device. If a MP-C control interface is the selected interface unused lines on the PIA will be strobed to turn on the punch function of a SWTPC AC-30 or equivalent tape interface. (See the PIA Strobing section for more information.) When the punch is completed a PUNCH OFF (1416) control character will be output and another PIA line will be strobed. User control is then returned to SWTBUG. To complete the tape making procedure you will have to enter the end of tape command described below.

END OF TAPE COMMAND E

The E command will punch the contents of the program counter (A048-A049) and an S9 to tape. The S9 is decoded by the load routine as an “end of tape” marker. For example, if you wish to save a program that resides from 0000 to 000F and whose starting address is 0005 you would perform the following sequence:

$M A002
$A002 FC		00
$A003	3E	00
$A004	A0	00
$A005	49	0F
$A006	4C

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