PC87334VLJ datasheet(11/102 Pages) NSC

11 / 102 page

10 Pin Description (Continued)

Symbol

PQFP

TQFP

Function

DCD12

77 69

75 67

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

Mode

density (525 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 e step in inactive e step out) during a seek operation During reads or

Mode

writes DIR is inactive

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

42 43

Drive SeIect 01

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

Digital Output Register bits D0 D1 The Drive Select outputs are gated with DOR bits 4 – 7

Mode

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 (See MTR01 for more information) DR0

exchanges logical drive values with 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

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

Mode

signal is active low (See ACK and Table 7-5 for further information)

DRATE01

Normal

52 51

50 49

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

Mode

written to last) The pins are totem-pole buffered outputs (6 mA sink 6 mA source)

DRATE0

PPM

Data Rate 0

This pin provides an additional Data Rate signal in PPM mode when PNF e 0

(See PD6 and Table 7-5 for further information)

Mode

DRID01

59 56

54 54

Drive ID

These pins accept input from the floppy disk drive which indicates the type of drive

in use These pins should be tied low if they are not used DRID1 is configured when bit 2 of

ASC is 1 and bit 1 of ASC is 0 (See IOCS16 IDEACK IDEHI VLD0 3F3RD IRTX and IRRX

for further information)

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)

DR23

Drive 2 or 3

DR23 is asserted when either Drive 2 or Drive 3 is accessed (except during

logical drive exchange see bit 3 of TDR) This pin is configured when bit 1 of ASC is 0 (See

DRV2 and PNF for further information)

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