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W83877TF

W83877TF首页预览图
型号: W83877TF
PDF文件:
  • W83877TF PDF文件
  • W83877TF PDF在线浏览
功能描述: WINBOND I/O
PDF文件大小: 968.02 Kbytes
PDF页数: 共154页
制造商: WINBOND[Winbond]
制造商LOGO: WINBOND[Winbond] LOGO
制造商网址: http://www.winbond.com
捡单宝W83877TF
PDF页面索引
120%
W83877TF/W83877TG
Publication Release Date: May 2006
-15- Revision 0.7
5. FDC FUNCTIONAL DESCRIPTION
5.1 W83877TF/TG FDC
The floppy disk controller of W83877TF/TG integrates all of the logic required for floppy disk control.
The FDC implements a PC/AT or PS/2 solution. All programmable options default to compatible
values. The FIFO provides better system performance in multi-master systems. The digital data
separator supports up to data rate 1 M bits/sec. (2 M bits/sec for fast tape drive)
The FDC includes the following blocks: AT interface, Precompensation, Data Rate Selection, Digital
Data Separator, FIFO, and FDC Core.
5.1.1 AT interface
The interface consists of the standard asynchronous signals: RD , WR , A0-A3, IRQ, DMA control,
and a data bus. The address lines select between the configuration registers, the FIFO and
control/status registers. This interface can be switched between PC/AT, Model 30, or PS/2 normal
modes. The PS/2 register sets are a superset of the registers found in a PC/AT.
5.1.2 FIFO (Data)
The FIFO is 16 bytes in size and has programmable threshold values. All command parameter
information and disk data transfers go through the FIFO. Data transfers are governed by the RQM and
DIO bits in the Main Status Register.
The FIFO defaults to disabled mode after any form of reset. This maintains PC/AT hardware
compatibility. The default values can be changed through the CONFIGURE command. The advantage
of the FIFO is that it allows the system a larger DMA latency without causing disk errors. The following
tables give several examples of the delays with a FIFO. The data are based upon the following
formula:
THRESHOLD
× (1/Data Rate) *8 - 1.5 μS = DELAY
FIFO THRESHOLD MAXIMUM DELAY TO SERVICING AT 500K BPS
Data Rate
1 Byte
1
× 16 μS - 1.5 μS = 14.5 μS
2 Byte
2
× 16 μS - 1.5 μS = 30.5 μS
8 Byte
8
× 16 μS - 1.5 μS = 6.5 μS
15 Byte
15
× 16 μS - 1.5 μS = 238.5 μS
FIFO THRESHOLD MAXIMUM DELAY TO SERVICING AT 1M BPS
Data Rate
1 Byte
1
× 8 μS - 1.5 μS = 6.5 μS
2 Byte
2
× 8 μS - 1.5 μS = 14.5 μS
8 Byte
8
× 8 μS - 1.5 μS = 62.5 μS
15 Byte
15
× 8 μS - 1.5 μS = 118.5 μS
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