AM3270/TR3271 Reference Manual

Details of the CRT Protocol

TR3271 Subdevice Protocols

086705 Tandem Computers Incorporated 6–7

SETMODE 59 Detail

CALL SETMODE (filenumber, 59, , ,params);

filenumber

an INT:value—is the file number returned by the OPEN for the subdevice.

an INT:value—is the SETMODE number for obtaining the actual count of the

bytes read.

params

is passed by reference (INT:ref:2), must be provided, and returns:

params[0] actual number of bytes read.

params[1] 0 (zero).

Note that the parameter positions normally used for param1 and param2 must not

be provided. If they are, a file-system error 2 (invalid operation attempted) will be

returned to the caller. Error 26 will be returned if the subdevice has no

outstanding two-step READs completed or if the SETMODE requester is not the

two-step READ requester.

The following is a functional example of the application request sequence using a two-

step READ and a SETMODE 59:

CALL OPEN (T^NAME,T1,FLAGS); open the subdevice.

CALL CONTROL (T1,22,500); post a 500-byte READ to T1

CALL AWAITIO (T1, ... ); and wait for completion.

CALL SETMODE (T1,59,,,PARAMS); the read has completed; get

. the actual size.

CALL READ(T1,BUFFER,PARAMS[0]); READ has completed with the

. actual byte size rather

. than 500.

WRITE Request

A WRITE request causes the subdevice to be flagged as “writing.” When the host

issues either a general poll to the control unit to which the writing subdevice is

logically connected, or a specific poll to the subdevice, TR3271 blocks and formats the

text unless certain status conditions exist. TR3271 then sends the text to the host a