參數(shù)資料
型號: 37C669
廠商: SMSC Corporation
英文描述: DIODE SCHOTTKY SINGLE 25V 200mW 0.5V-vf 200mA-IFM 30mA-IF 2uA-IR SOD-323 3K/REEL
中文描述: 電腦98/99順從超級I / O軟盤控制器與紅外線支持
文件頁數(shù): 87/164頁
文件大?。?/td> 621K
代理商: 37C669
29
MAIN STATUS REGISTER
Address 3F4 READ ONLY
The Main Status Register is a read-only register
and indicates the status of the disk controller.
The Main Status Register can be read at any
time.
The
MSR
indicates
when
the
disk
controller is ready to receive data via the Data
Register.
It should be read before each byte
transferring to or from the data register except in
DMA mode. NO delay is required when reading
the MSR after a data transfer.
BIT 0 - 3 DRV x BUSY
These bits are set to 1s when a drive is in the
seek portion of a command, including implied
and overlapped seeks and recalibrates.
BIT 4 COMMAND BUSY
This bit is set to a 1 when a command is in
progress.
This bit will go active after the
command byte has been accepted and goes
inactive at the end of the results phase. If there
is
no
result
phase
(Seek,
Recalibrate
commands), this bit is returned to a 0 after the
last command byte.
BIT 5 NON-DMA
This
mode
is
selected
in
the
SPECIFY
command and will be set to a 1 during the
execution phase of a command.
This is for
polled data transfers and helps differentiate
between the data transfer phase and the reading
of result bytes.
BIT 6 DIO
Indicates the direction of a data transfer once a
RQM is set.
A 1 indicates a read and a 0
indicates a write is required.
BIT 7 RQM
Indicates that the host can transfer data if set to
a 1. No access is permitted if set to a 0.
7
6
5
4
3
2
1
0
RQM
DIO
NON
DMA
CMD
BUSY
DRV3
BUSY
DRV2
BUSY
DRV1
BUSY
DRV0
BUSY
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