Bit Assignment - Status Lines; User-Writeable Control Lines; Bit Assignment - Control Lines - Fluke 9000A-8080 Instruction Manual

8080
• User-writable control lines
• Bit number assignment of control lines
• Address space assignment
• Pin assignments
These assignments are described in the following paragraphs and are
summarized for convenience on the pod decal.
3-5.
Bit Assignment - Status Lines
When a read status (READ
@
STS) operation is performed, the troubleshooter
displays the result in binary form, where a "l" indicates a logic high status line.
To determine which bits of the displayed read status correspond to specific
status lines, each line has an assigned bit number, as listed in Table 3-2. Bit
number zero (READ) appears at the far right of the display, while bit number 7
(POWER FAIL) appears at the far right.
For example, if the READY (bit number 0) and POWER FAIL (bit number 7)
lines are low, and the other status lines are high, the troubleshooter would read
READ
@
STS
=
0001 1010 OK. Bit numbers 0 (READY) and 7 (POWER
FAIL) are zero to indicate a logic low, while other meaningful bits are ones to
indicate logic high. Bits 2, 5 and 6, which have no meaning for 8080 status lines,
are always represented by zeros in the troubleshooter display message.
3-6.
User-Writeable Control Lines
The 8080 has three control lines which the troubleshooter can write to. These
lines are interrupt enable (INTE), wait (WAIT) and hold acknowledge (HLDA).
To write to any or all of these lines, a WRITE CTL function is used as described
in the paragraphs that follow. Note that writing to a control line only sets the line
to the high or low state for approximately 20 microseconds; just long enough to
verify that it can be driven.
3-7.
Bit Assignment - Control Lines
There are two troubleshooting functions which require the entry of binary digits
to identify user-writeable control lines. These functions include write control
(WRITE
@
CTL) and data toggle control (DTOG
@
CTL).
When performing or programming either of these two functions, the user is
prompted for a binary number to identify the control line(s) to be written,
HLDA, WAIT, and INTE. Table 3-2 shows that these lines have bit numbers 0,
1 and 2 respectively. To perform a write control operation on these three lines,
3-4