B-22. Function Name: READST

Purpose: Read status word
Call address: $FFB7 (hex) 65463 (decimal)
Communication registers: A
Preparatory routines: None
Error returns: None
Stack requirements: 2
Registers affected: A

Description: This routine returns the current status of the I/O devices in the accumulator. The routine is usually called after new communication to an I/O device. The routine gives you information about device status, or errors that have occurred during the I/O operation.

The bits returned in the accumulator contain the following information: (see table below)

ST BIT POSITION	ST NUMERIC VALUE	CASETTE READ	SERIAL/RW	TAPE VERIFY + LOAD
0	0		Time out write
1	2		Time out read
2	4	Short block		Short block
3	8	Long block		Long block
4	16	Unrecoverable read error		Any mismatch
5	32	Checksum error		Checksum error
6	64	End of file	EOI line
7	-128	End of tape	Device not present	End of tape

How to Use:

1. Call this routine.
2. Decode the information in the A register as it refers to your program.

EXAMPLE:

   ;CHECK FOR END OF FILE DURING READ
   JSR READST
   AND #64                       ;CHECK EOF BIT (EOF=END OF FILE)
   BNE EOF                       ;BRANCH ON EOF