SCD1283 datasheet(38/94 Pages) INTEL

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CD1283 — IEEE 1284-Compatible Parallel Interface

Datasheet

5.5.6

Manual Mode

Manual mode allows direct control of the five output control signals and the PD bus. It is not

intended for data transfers, but rather for advanced diagnostics. Enter Manual mode by setting the

ManMd bit (PCR[7]) when the interface is in Compatibility mode.

The MMDir bit (PCR[1]) sets the direction of the PD bus: 0

= input; 1 = output. When the MMDir

bit is set to ‘1’, data for the PD bus comes from the MDR. The ManOE bit controls the tristate

buffer on the PD bus: 0

= floating; 1 = driving. When MMDir is ‘0’, ManOE is ignored, PD[7:0]

are inputs, and the data can be read in the MDR.

5.5.7

Control Signals

Output signals are controlled by the OVR. The degree of control depends on the current mode. In

Manual mode, all five signals are under user control. In Compatible and EPP modes, only three

signals are available, the others are set by the state machine.

IVR, ZDR, ODR, and SSR monitor the four input signals. These four registers have a common

format. The IVR always shows the values of the four input pins. ZDR and ODR allow the user to

force interrupts on specific signal transitions. Bits set in the ZDR generate an interrupt, if the

specified signal changes from ‘1’ to ‘0’. Similarly, bits set in the ODR generate an interrupt if the

specified signal changes from ‘0’ to ‘1’. When both bits are set, interrupts are generated on either

transition. The SSR shows the status of signal changes according to ZDR and ODR. SSR shows

which signal changed. (It is necessary for the user to read the IVR to determine how the signal

changed.) The signal change interrupt is enabled with the SigCh bit (PCIER[4]).

Figure 8. FIFO Data Path Functional Diagram: Transmit

DB[15:8]

DB[7:0]

(TRANSMIT)

FIFO (64 BYTES)

TAG (64 BITS)

PFSR

TAG

TAG BIT

STATUS

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