Fluke 2180A - Manual (Page 71)

21X0A-004
rocessors ensures that they are synchronized properly with
the IEEE-488 interface chip (U12), and is a recommended
start-up procedure at the beginning of the program in the
IEEE-488 controller. A 2 second time delay is required to
complete the resetting operation. Do not attempt to access
Option 21X0A-004 before the end of the time delay.
604-24. Functional Equivalent
604-25. The operation of Option 21XOA-004 is functionally
equivalent to the combination of the Fluke 21X0A-002,
2XXXA-522, and I120A with the exception of the follow­
ing four items:
CHANGES:
1. Option 21X0A-004 displays a lower case (d)
instead of a blank in front of the temperature
scale indicator. See Output Format, Table 604-3.
2. Option 21XO A-004 operates at the full speed rate
of the thermometer, (3 readings per second,
instead of 1.5 readings per second).
3. The 2XXXA-522 previously contained a buffer-
full SRQ function that produced an SRQ when
the 32-byte buffer is filled. The buffer-full SRQ
function no longer exists with the 2XXXA-522,
but the switch is still present and its function is
still listed in the 2XXXA-522 manual. The
buffer-full SRQ function is not available on
Option 21X0A-004.
ADDED
FEATURE:
(DCLK-) clocks the accessory bus address then the ther­
mometer data into the 3870 microprocessor (U5) on the
DATA- line. In U5, the data is formatted (Table 604-2) and
made available for transfer to the 8748 microprocessor
(Ull).
604-29. U5 applies a character to the tri-state buffers (U8
and U9) and pulls the Data Valid (DATVAL) line low. If
Ull is not transferring data to UI2 or if it is waiting for
SRQ to be serviced, Ull responds to U5 by strobing the
character onto the Option Data Bus with a STROBE- sig­
nal and reads the character into its 32-byte buffer. U11 also
generates Acknowledge (ACK), which causes U5 to reply
with a new character. When an LF character is detected,
Ull unmasks the byte-out interrupt. If the SRQ switch is
set to ON, the SRQ switch triggers the GPIA (General
Purpose Interface Adapter) to send SRQ to the controller.
The 32-byte buffer never completely fills because ther­
mometer readings consist of 21 bytes.
604-30. The IEEE-488 Bus Controller initiates the talk
mode by sending the talk address to the GPIA (U12) over
the IEEE-488 bus when Attention (ATN) is asserted true
low. The GPIA responds by setting the byte-out interrupt
(U12-40) high, as a signal to U11 to pass data bytes to U12.
The following three conditions must be met before data
transfer can begin:
® Ready For Data (RFD) from the IEEE-488 bus
is true (low).
• Data Accepted (DAC) from the IEEE-488 bus is
false (high).
® Ull must have the byte-out interrupt unmasked.
4. Option 21 XO A-004 responds to a Group Execute
Trigger. See Group Execute Trigger, paragraph
604-23.
604-26. If you include Option 21X0A-004 when up­
grading or adding new equipment to a system currently
operating with the 21X0A-002, 2XXXA-522, or 1120A
combination, note the first two changes listed in paragraph
604-25.
604-27. THEORY OF OPERATION
604-28. Option 21X0A-004 converts the temperature dis­
played by the thermometer into a format usable by an
IEEE-488 Bus Controller. Option 21X0A-004 communi­
cates with the thermometer on the clocked bit-serial acces­
sory bus. The channel number, range, conversion type,
scale, and digits of the temperature reading are transmitted
on the bus. The cycle is repeated every 333 ms. When the
Write Address (WRTADR-) line is held low. Data Clock
604-31. When the above conditions are met, UII sends
the data byte to the Data Out Register of the GPIA via the
Option Data Bus. At this time, the byte-out interrupt is set
to zero, and the data byte is checked for the LF character.
The GPIA handshakes the data byte to the IEEE-488 Bus,
and the byte-out interrupt (U12-40), transmitted to UT1, is
set to 1. If the data byte is an LF character, EOI (End or
Identify) is also sent to the IEEE Controller to signal the
end of a data reading. This process continues as long as
there is data in the 32-byte buffer of U11. When the 32-byte
buffer is empty, Ull masks the byte-out interrupt from the
GPIA.
604-32. The IEEE-488 address setting for Option 21XOA-
004 is read by the GPIA (U12) via the Option 21X0A-004
data bus when the GPIA sends a strobe out on U12-4 to the
address switch tri-state buffers (U18).
604-33. When the GPIA detects a Group Execute Trigger
for its address, it sets U12-24 to a logic high to cause a
604-5