Bit Mnemonic Description
1-0w ADM[1-0] Address Mode Bits 1 through 0
These bits state the addressing mode currently in effect–that is, the
manner in which the information in ADR0 and ADR1 is interpreted
(see Address Register 0 and Address Register 1 later in this chapter).
If both bits are zero, then the TLC does not respond to GPIB address
commands. Instead, the ton and lon bits are used to program the
Talker and Listener functions, respectively. The ton and lon bits must
be cleared if mode 1, 2, or 3 addressing is selected, and the ADM1
through 0 bits must be cleared if either of the bits ton or lon are set.
Mode ADM1 ADM0 Title
0 0 0 ton/lon
1 0 1 Normal dual addressing
2 1 0 Extended single addressing
3 1 1 Extended dual addressing
In mode 1, ADR0 and ADR1 contain the major and minor addresses,
respectively, for dual primary GPIB address applications; that is, the
TLC responds to two GPIB addresses: a major address and a minor
address. The MJMN bit in the ADSR indicates which address was
received. In applications where the TLC needs to respond to only one
address, the major Talker and Listener function is used and the minor
Talker and Listener function should be disabled. The minor Talker
and Listener function can be disabled by setting the Disable Talker
(DT) and Disable Listener (DL) bits in ADR1 (set ADR and ADR1).
In mode 2 (ADM1=1, ADM0=0), the TLC recognizes two sequential
GPIB address bytes, a primary followed by a secondary. Both GPIB
address bytes must be received in order to enable the TLC to talk or
listen. In this manner, mode 2 addressing uses the Extended Talker
and Extended Listener functions as defined in IEEE 488, without
requiring computer program intervention. In mode 2, ADR0 and
ADR1 contain the TLC primary and secondary GPIB addresses,
respectively.
In mode 3 (ADM1=1, ADM0=1), the TLC handles addressing just as
it does in mode 1, except that each major or minor GPIB primary
address must be followed by a secondary address. All secondary
GPIB addresses must be verified by computer program when mode 3
is used. When the TLC is in Talker Primary Addressed State (TPAS)
or Listener Primary Addressed State (LPAS) and a secondary address
byte is on the GPIB DIO lines, the APT bit of ISR2 is set and the
secondary GPIB address may be inspected in the CPTR. The TLC
Acceptor Handshake is held up in the Accept Data State (ACDS) until
the Valid or Non-Valid auxiliary command is written to the AUXMR,
signaling a valid or invalid secondary address, respectively, to the
TLC.