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Table 2-10
NS87336VLJ Pin Descriptions (continued)
Pin
No.
DENSEL
48
(Normal Mode)
DENSEL
78
(PPM Mode)
/DIR
41
(Normal Mode)
/DIR
80
(PPM Mode)
/DR0,
44, 45
/DR1
(Normal Mode)
/DR1
85
(PPM Mode)
/DR23
49
/DRATE0
52, 51
/DRATE1
(Normal Mode)
/DRATE0
87
(PPM Mode)
DRQ0
56
DRQ1
33
DRQ2
4
I/O
Description
O
FDC Density Select. DENSEL indicates that a high FDC density
data rate (500 Kbs, 1 Mbs or 2 Mbs) or a low density data rate (250
or 300 Kbs) is selected. DENSEL is active high for high density
(5.25-inch drives) when IDENT is high, and active low for high density
(3.5-inch drives) when IDENT is low. DENSEL is also programmable
via the Mode command.
O
FDC Density Select. This pin offers an additional Density Select
signal in PPM Mode when PNF=0.
O
FDC Direction. This output determines the direction of the floppy
disk drive (FDD) head movement (active = step-in; inactive = step-
out) during a seek operation. During reads or writes, DIR is inactive.
O
FDC Direction. This pin offers an additional Direction signal in PPM
Mode when PNF = 0.
O
FDC Drive Select 0, 1. These are the decoded drive select outputs
that are controlled by Digital Output Register bits D0, D1. The Drive
Select outputs are gated with DOR bits 4-7. These are active low
outputs. They are encoded with information to control four FDDs
when bit 4 of the Function Enable Register (FER) is set.
exchanges logical drive values with DR1 when bit 4 of Function
Control Register is set.
O
FDC Drive Select 1. This pin offers an additional Drive Select signal
in PPM Mode when PNF = 0. It is drive select 1 when bit 4 of FCR is
0. It is drive select 0 when bit 4 of FCR is 1. This signal is active
low.
O
FDC Drive 2 or 3. /DR23 is asserted when either Drive 2 or Drive 3
is assessed(except during logical drive exchange).
O
FDC Data Rate 0, 1. These outputs reflect the currently selected
FDC data rate (bits 0 and 1 in the Configuration Control Register
(CCR) or the Data Rate Select Register (DSR), whichever was written
to last). The pins are totem-pole buffered outputs (6 mA sink, 6 mA
source).
O
FDC Data Rate 0. This pin provides an additional Data Rate signal,
in PPM mode, When PNF=0.
O
DMA Request 0, 1, 2.
controller that a data transfer is required. This DMA request can be
sourced by one of the following: FDC or Parallel Port.
When it is not
the sourced device is disabled or when the sourced device is
configured with no DMA, it is also in TRI-STATE. Upon reset, DRQ2
is used by the FDC.
\An active high output that signals the DMA
sourced by and of them, it is in TRI-STATE. When
DR0
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