PCM16C00 datasheet(21/40 Pages) NSC

21 / 40 page

60 Operational Modes (Continued)

INTERRUPT PROTOCOL

The interrupt protocol is defined in the Function Configura-

tion Status Register descriptions When operating in a multi-

function environment the PCM16C00 may be placed in an

interrupt mode where IREQ

is an ‘‘or’’ of the two CINT( )s

or where the enhanced interrupt protocol is used The se-

lection of either mode is done using the IntrReset bit in the

Function Configuration Status Registers For multi-function

operation it’s recommended that system software place the

PCM16C00 in the enhanced mode (IntrReset bits set to one

(1)) This insures that interrupts can be generated by either

function and that they will not be missed by the standard

PC-compatible interrupt controller Of course either pulse

or level mode interrupts may be selected Once an interrupt

occurs the first system software to be called is the interrupt

handler How this software determines which function gen-

erated the interrupt is outside the scope of an IC datasheet

however mechanisms do exist For example software may

be written to read the FCSRs to determine the function

Software could also be written to make no determination if it

is not required for the particular functions Finally software

could be written that works in conjunction with the function-

specific device interrupt handlers to determine which func-

tion requires service without explicitly reading the FCSRs on

the PCM16C00 In either case system software is responsi-

ble for writing a zero (0) to one of the PCM16C00’s Intr bits

in an FCSR once interrupt processing is done if the

PCM16C00 is using enhanced interrupts (IntrReset is set to

one (1)) This informs the PCM16C00 that it may generate

another interrupt if one is pending that will be recognized

by the PC-compatible interrupt controller in either pulse or

level mode

BACKWARD COMPATIBILITY

The PCM16C00 may be operated as a single function

PCMCIA interface by using Function 0 only In this case the

CIS or system software should be written to only configure

function 0

PCM16C00 Datasheet(PDF) 21 Page - National Semiconductor (TI)