Intel mcs-48 manual Usa, Status Registers BIT Name Symbol Description

inter8272

TABLE 8. STATUS REGISTERS
	BIT
NO.	NAME	SYMBOL	DESCRIPTION
		STATUS REGISTER 0
0 7	Interrupt	IC	D7~Oand Ds~O
	Code		Normal Termination of Command,
			(NT). Command was completed and
			properly executed.
Os			07=0 and Ds='
			Abnormal Termination of Com·
			mand, (AT). Execution of Command
			was started, but was not
			successfully completed.
			0 7='and Ds=O
			Invalid Command issue, (I C).
			Command which was issued was
			never started.
			0 7='and Ds='
			Abnormal Termination because
			during command execution the
			ready signal from FDD changed
			state.
0 5	Seek End	SE	When the FDC completes the
			SEEK Command, this flag Is set to ,
			(high).
0 4	Equipment	EC	If a fault Signal is received from the
	Check		FDD, or If the Track 0 Signal fails to
			occur after 77 Step Pulses (Recali·
			brate Command) then this flag Is set.
0 3	Not Ready	NR	When the FDD is in the not·ready
			state and a read or write command is

	BIT
NO.	NAME	SYMBOL	DESCRIPTION
		STAtUS RE.GISTER , (CONT.)
0,	Not	NW	During execution of WRITE DATA,
	Writable		WRITE DELETED DATA or Format A
			Cylinder Command, If the FDC
			detects a write protect signal from
			the FDD, then this flag Is set.
Do	MISSing	MA	If tlie FDC cannot detect the 10
	Address		Address Mark after encountering the
	Mark		Index hole twice, then this flag is set.
			If the FOC cannot detect the Data
			Address Mark or Deleted Data
			Address Mark, this flag Is set. Also
			at the sam.e time, the MD (Missing
			Address Mark in Data Field) of
			Status Register 2 is set.
		STATUS REGISTER 2
0 7			Not used. This bit is always 0 (low).
			----
0 6	Control	CM	During executing the READ DATA or
	Mark		SCAN Command, if the FOC
			encounters a Sector which contains
			a Deleted Data Address Mark, this
			flag is set.
0 5	Data Error in	00	If the FOC detects a CRC error In
	Data Field		the data field then this flag is set.
0 4	Wrong	WC	This bit is related with the NO bit,
	Cylinder		and when the contents of C on the
			medium is different from that stored

O2 Head

Address

0, Unit Select'

Do Unit SelectO

07 End of Cylinder

Os

05Data Erwr

04 Over Run

	issued, this flag Is set. If a read or
	write command is issued to Side 1
	of a single sided drive, then this flag
	is set.
HD	This flag is used to Indicate the
	state of the head at Interrupt.
US,	These flags are used to indicate a
usa	Drive Unit Number at Interrupt
STATUS REGISTER'
EN	When the FDC tries to access a
	Sector beyond the final Sector of a
	Cylinder, this flag Is set.
	Not used. This bit is always 0 (low).
DE	When the FDC detects a CRC error
	In either the 10 field or the data field,
	this flag Is set.
OR	If the FDC Is not serviced by the
	main-systems during data transfers,
	within a certain time Interval, this
	flag Is set.

			In the lOR, this flag is set.
0 3	Scan Equal	SH	During execution, the SCAN
	Hit		Command, if the condition of
			"equal" is satiSfied, this flag is set.
O2	Scan Not	SN	During executing the SCAN
	Satisfied		Command, If the FDC cannot find a
			Sector on the cylinder which meets
			the condition, then this flag is set.
0,	Bad	BC	This bit is related with the NO bit,
	Cylinder		and when the content of C on the
			medium is different from that stored
			In the lOR and the content of C is
			FF, then this flag is set.
Do	Missing	MD	When data Is read from the medium,
	Address		If the FOC cannot find a Data
	Mark In Data		Address Mark or Deleted Data
	Field		Address Mark, then this flag Is set.
		STATUS REGISTER 3
0 7	Fault	FT	This bit Is used I" indicate the
			status of the Fault signal from the
			FDO.

0 3

O2 No Data

	Not used. This bit always 0 (low).
NO	During execution of READ DATA,
	WRITE DELETED DATA or SCAN

Command, If the FDC cannot find the Sector specified in the lOR Register, this flag is set.

During executing the READ 10 Com· mand, if the FDC cannot read the

10 field without an error, then this flag is set.

During the execution of the READ A Cylinder Command, if the starting sector cannot be found, then this flag is set.

Os	Write	WP
	Protected
0 5	Ready	ROY
0 4	Track 0	TO
0 3	Two Side	TS
02	Head	HO
	Address
0,	Unit Select'	US,

This bit Is used to indicate the status of the Write Protected Signal from the FDO.

This bit is used to indicate the status of the Ready signal from the FDD.

This bit is used to indicate the status of the Track 0 signal from the FOO.

This bit is used to indicate the status of the Two Side signal from the FDD.

This bit is used to indicate the status of Side Select signal to the FDD.

This bit is used to Indicate the status of the Unit Select'signal tothe FDD.

Do Unit Select 0	usa	This bit is used to indicate the status
		of the Unit Select 0 signal tothe FDD.

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