參數資料
型號: UPD765A
廠商: NEC Corp.
英文描述: Single/Double Density Floppy-Disk Controller
中文描述: 單/雙密度軟盤控制器
文件頁數: 5/17頁
文件大?。?/td> 344K
代理商: UPD765A
NEC
uPD765A/uPD765B
DIFFERENCES BETWEEN
,uPD765A
AND
uP D765B
The uPD765B
is a
functionally enhanced version of the
uPD765A.
Differences are explained below.
Overrun Bit [OR]
In
uPD765A,
when executing a read- or write-type
command (except READ ID and SCAN types), the
result status OR bit is not set if there is an overrun on
the final byte of a sector. An improvement in the
uPD765B
allows it to set the OR bit in any situation.
DRQ
Reset
When an overrun occurs, the
uPD765A
needs DACK
input to reset DRQ. If DACK is not available, an
external DMA controller continues to operate even after
the
FDC
enters the R-Phase (Result Phase), and stored
result status may be transferred accidentally as ordinary
data.
On the other hand, the
uPD765B
resets
DRQ auto-
matically just before the R-Phaseentry and independent
of the DACK input. See AC Characteristics for DRQ
reset
timing.
Clock
The
between the CLK and WCLK inputs.
Synchronization
uPD765B
does not require synchronization
Version Command
The Version command distinguishes the
uPD765B
from other devices. The
ST0
response to the Version
command is:
Part No.
ST0
Value
uPD765A
uPD765B
80H
90H
5-7
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