PC87332VLJ datasheet(10/98 Pages) NSC

10 / 98 page

10 Pin Description (Continued)

Symbol

Function

DCD12

77 69

Data Carrier Detect

When low this signal indicates that the MODEM or data set has detected the

data carrierThe DCD signal is a MODEM status input whose condition the CPU can test by reading bit

7 (DCD) of the MODEM Status Register (MSR) for the appropriate serial channel Bit 7 is the

complement of the DCD signal Bit 3 (DDCD) of the MSR indicates whether the DCD input has

changed state since the previous reading of the MSR

Note

Whenever the DDCD bit of the MSR is set an interrupt is generated if MODEM Status interrupts are enabled

DENSEL

Normal

Density Select

Indicates that a high FDC density data rate (500 kbps 1 Mbps or 2 Mbps) or a low

density data rate (250 kbps or 300 kbps) is selected DENSEL is active high for high density (525

Mode

drives) when IDENT is high and active low for high density (35 drives) when IDENT is low DENSEL

is also programmable via the Mode command (see Section 426)

DENSEL

PPM

Density Select

This pin provides an additional Density Select signal in PPM Mode when PNF e 0

(See AFD and Table 7-5 for further information)

Mode

DIR

Normal

Direction

This output determines the direction of the floppy disk drive (FDD) head movement (active

step in inactive e step out) during a seek operation During reads or writes DIR is inactive

Mode

DIR

PPM

Direction

This pin provides an additional direction signal in PPM Mode when PNF e 0 (See INIT and

Table 7-5 for further information)

Mode

DR01

Normal

44 45

Drive SeIect 01

These are the decoded Drive Select outputs that are controlled by the Digital Output

Mode

outputs They are encoded with information to control four FDDs when bit 4 of the Function Enable

DR1 when bit 4 of Function Control Register (FCR) is set (See Table 7-5 for further information)

DR1

PPM

Drive Select 1

This pin provides an additional Drive Select signal in PPM Mode when PNF e 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

Mode

(See ACK and Table 7-5 for further information)

DRATE01

52 51

Data Rate 01

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)

DRV2

Drive2

This input indicates whether a second floppy disk drive has been installed The state of this

pin is available from Status Register A in PS2 mode (See PNF for further information)

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