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參數資料
| 型號： | W83877AF |
| 廠商： | WINBOND ELECTRONICS CORP |
| 元件分類： | 外設及接口 |
| 英文描述： | Multi-Function I/O Port Controller(多功能輸入／輸出口控制器) |
| 中文描述： | MULTIFUNCTION PERIPHERAL, PQFP100 |
| 封裝： | QFP-100 |
| 文件頁數： | 22/171頁 |
| 文件大小： | 1634K |
| 代理商： | W83877AF |
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W83877AF
Publication Release Date: Dec. 1996
Preliminary Version 0.52
- 20 -
At the start of a command the FIFO is always disabled and command parameters must be sent based
upon the RQM and DIO bit settings in the main status register. When the FDC enters the command
execution phase, it clears the FIFO of any data to ensure that invalid data are not transferred.
An overrun and underrun will terminate the current command and the data transfer. Disk writes will
complete the current sector by generating a 00 pattern and valid CRC. Reads require the host to
remove the remaining data so that the result phase may be entered.
DMA transfers are enabled with the SPECIFY command and are initiated by the FDC by activating
the DRQ pin during a data transfer command. The FIFO is enabled directly by asserting DACK and
addresses need not be valid.
Note that if the DMA controller is programmed to function in verify mode a pseudo read is performed
by the FDC based only on DACK. This mode is only available when the FDC has been configured
into byte mode (FIFO disabled) and is programmed to do a read. With the FIFO enabled the above
operation is performed by using the new VERIFY command. No DMA operation is needed.
@
2.1.3 Data Separator
The function of the data separator is to lock onto the incoming serial read data. When a lock is
achieved the serial front end logic of the chip is provided with a clock which is synchronized to the
read data. The synchronized clock, called the Data Window, is used to internally sample the serial
data portion of the bit cell, and the alternate state samples the clock portion. Serial to parallel
conversion logic separates the read data into clock and data bytes.
The Digital Data Separator (DDS) has three parts: control logic, error adjustment, and speed tracking.
The DDS circuit cycles once every 12 clock cycles ideally. Any data pulse input will be synchronized
and then adjusted by immediate error adjustment. The control logic will generate RDD and RWD for
every pulse input. During any cycle where no data pulse is present, the DDS cycles are based on
speed. A digital integrator is used to keep track of the speed changes in the input data stream.
2.1.4 Write Precompensation
The write precompensation logic is used to minimize bit shifts in the RDDATA stream from the disk
drive. Shifting of bits is a known phenomenon in magnetic media and is dependent on the disk media
and the floppy drive.
The FDC monitors the bit stream that is being sent to the drive. The data patterns that require
precompensation are well known. Depending upon the pattern, the bit is shifted either early or late
relative to the surrounding bits.
2.1.5 Perpendicular Recording Mode
The FDC is also capable of interfacing directly to perpendicular recording floppy drives. Perpendicular
recording differs from the traditional longitudinal method in that the magnetic bits are oriented
vertically. This scheme packs more data bits into the same area.
FDCs with perpendicular recording drives can read standard 3.5" floppy disks and can read and write
perpendicular media. Some manufacturers offer drives that can read and write standard and
perpendicular media in a perpendicular media drive.
A single command puts the FDC into perpendicular mode. All other commands operate as they
normally do. The perpendicular mode requires a 1 Mbps data rate for the FDC. At this data rate the
FIFO eases the host interface bottleneck due to the speed of data transfer to or from the disk.
相關PDF資料 |
PDF描述 |
|---|---|
| W83877ATD | enhanced version from Winbonds most popular I/O chip W83877F |
| W83877ATF | enhanced version from Winbonds most popular I/O chip W83877F |
| W83877 | WINBOND I/O |
| W83877F | WINBOND I/O |
| W83877TD | I/O chip disk drive adapter |
相關代理商/技術參數 |
參數描述 |
|---|---|
| W83877ATD | 制造商:WINBOND 制造商全稱:Winbond 功能描述:enhanced version from Winbonds most popular I/O chip W83877F |
| W83877ATF | 制造商:WINBOND 制造商全稱:Winbond 功能描述:enhanced version from Winbonds most popular I/O chip W83877F |
| W83877F | 制造商:WINBOND 制造商全稱:Winbond 功能描述:WINBOND I/O |
| W83877TD | 制造商:WINBOND 制造商全稱:Winbond 功能描述:WINBOND I/O |
| W83877TF | 制造商:WINBOND 制造商全稱:Winbond 功能描述:WINBOND I/O |
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