National Instruments 320030-01

Chapter 5 Programming Considerations

Address Mode 2

Address Mode 2 is used when Talker Extended (TE) or Listener Extended (LE) functions are to

be used. TE and LE functions require receipt of two addresses (primary and secondary) before

setting TA or LA. The TLC GPIB primary address is indicated by the byte written to ADR0.

The secondary address is indicated by the byte written to ADR1. Upon receipt of both the

primary and secondary GPIB addresses, the TLC becomes an addressed Talker or Listener. If

the TLC has received its primary GPIB Talk address, the Talker Primary Addressed State

(TPAS) bit in the ADSR is set. If the TLC has received its primary GPIB Talk address

immediately followed by its secondary GPIB Talk address, the TA bit in the ADSR is set, the

ADSC bit in ISR2 is set, and the DO bit in ISR1 is set. If the TLC has received its Primary

GPIB Listen address, the LPAS bit in the ADSR is set. If the TLC has received its primary

GPIB Listen address immediately followed by its secondary GPIB Listen address, the LA bit in

the ADSR is set, the ADSC bit in ISR2 is set, and the DI bit in ISR1 is set when the first GPIB

data byte is received. The MJMN bit in the ADSR indicates whether the address status refers to

the major or minor address.

Address Mode 3

Address Mode 3, like Address Mode 2, is used to implement Extended GPIB Talk and Listen

address recognition. However, unlike Address Mode 2, Address Mode 3 provides for both major

and minor primary addresses, and your program must identify the secondary address by reading

the CPTR. Proper operation using Address Mode 3 is listed as follows:

1. During initialization of the TLC, enable Address Mode 3 (and optionally set the APT IE bit

in IMR1 to enable an interrupt request on receipt of a secondary GPIB address). Write the

TLC major GPIB primary address to ADR0 and the TLC minor GPIB primary address to

ADR1.

2. Receipt of the TLC major or minor primary GPIB Talk Address (MTA) or major or minor

primary GPIB Listen Address (MLA) sets TPAS or LPAS, indicating that the primary

address has been received.

3. If the next GPIB command following the primary address is a secondary address, the APT bit

is set and a DAC handshake holdoff is activated (the GPIB DAC message is held false).

4. In response to APT, the program must complete the following events:

• Determine whether the command just received is a listen, talk, major, or minor address by

reading the LPAS, TPAS, and MJMN bits of the ADSR.

• Read the secondary address in the CPTR and determine whether or not it is the address of

the TLC.

5. If it is not the TLC address, issue the Non-Valid auxiliary command. If it is the TLC address,

issue the Valid auxiliary command.