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WJ-8718A/MFP
INSTALLATION AND OPERATION
2.4.5.4.2
Monitor Data Format
A monitor program begins with the transmission of a receiver address word which
activates the I/O circuits in the addressed receiver, causing an interrupt signal to be generated
to the microprocessor in the receiver control block. The microprocessor-branches to an area of
memory containing the current receiver parameter data.
Receiver parameters are stored in
sequential memory locations in the order listed in Table
2-19.
The processor begins to transmit
data at the location where a previous data transmission ended.
The controller receives the
transmitted data in binary-coded form and has no way of knowing which data is represented by
the binary-coded transmissions.
To synchronize the transmission of data, an address header precedes the parameter
data words in memory.
The address header is an 8-bit word containing the 5-bit receiver
address in the lower-order bits. The 2 6 and 2 7 bits are high to uniquely identify the word as an
address header (2 5 bit is irrelevant).
After the address header has been transmitted and
identified, the eight data words that follow will be the parameter data listed in Table
2-19.
The programmer uses a comparison technique to identify or I1findl1 the address
header.
The first two bits of the binary-coded word are high (llXXXXXX); therefore, the
decimal equivalent of the address header word is always greater than 192. The parameter data
binary codes are such that the 2 MSDs are never high at the same time; thus, the decimal
equivalent of a parameter data word will always be less than 192. By successively comparing
the decimal equivalent of each transmitted word to 192, the address header can be isolated and
the data words identified.
2.4.5.4.2.1
Remote Monitor Programming
Table
2-23
is a monitor program for the Hewlett-Packard 9825A Calculator. The
first four program steps (0 through 3) establish a string of 15 spaces (A $ [15] ) for placement of
parameter data, formatting the display readout, and loading zeros into locations I and A.
Program steps 4,
5,
and 6 establish two loops, or sets of program instructions, for
the identification of the address header and parameter data words and their storage in
consecutive locations.
Step 4 instructs the calculator to read the binary-coded data (rdb)
received on the 488 interface (7XX) from the equipment at address 06 (X06), and to place the
data word in register rl or rO (-rI). Step 5 examines registers A and rl, and, if A
=
0 and rl is
less than 192, repeats step 4. This procedure (loop) will repeat until the decimal equivalent of
the binary-coded data word stored in rl, is greater than 192 (the only data word greater than
192 is the address header word). At this point, the program jumps out of the loop to step 6.
In step 6, rl is incremented and A is loaded with a 1; if rl is less than 9 (rl is now 1),
the program returns to step 4. The received data word is read and placed in rl (now in rl, one
location away from the address header word in location rO) and the program advances to step
6.
Again, rl is incremented
(I +
1
=
I or 1
+
1
=
2
=
I) and the loop repeats until I
=
9, when the
program jumps out of the loop to step 7. The contents of rO are reduced by 192: at this point
rO contains the address and rl through 8 contain the receiver parameter data words in the order
listed in Table
2-19.
Program steps 8 through 22 are a combination of binary AND, shift, and compari-
son operations which isolate the information in the parameter data words.
For example, in
step 14, the contents of r6 (in Table
2-19,
the register
5
data) are ANDed with 31 (00011111),
2-30
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