HP 8920A - Page 409

409
Chapter 10, Signaling Encoder (AF Generator 2)
MPT 1327 Encoder
The control channel filler buffer comprises 32 individual timeslots. It is accessed only
through the HP-IB with the following command:
ENCoder:MPT1327:FILLer:DATA
n,string
Where
• n is the location selector and has the range 1 through 32.
• string is a string containing a signaling language command defining the content of one
timeslot. Some signaling language commands also define data codewords and therefore
translate to data for two or three timeslots. The signaling language commands take the
form of an assembly language.
NOTE: In MPT 1327 an address codeword can be followed by up to four data codewords. A data
codeword occupies half of one timeslot. The signaling language definition restricts the
firmware to accept only two or four data codewords. An odd number of data codewords must
be added to occupy a whole number of timeslots. For messages with an odd number of data
codewords the padding word must be generated by IBASIC.
An example of the format is given in the sequence of commands below. It defines
a two timeslot random access frame with a broadcast message, transmitted on
channel 212 of system 4901
16
.
ENC:MPT1327:FILL:DATA 1,’ALH 0,ALLI,212,0,0,2’
ENC:MPT1327:FILL:DATA 2,’ALH 0,ALLI,212,0,0,0’
ENC:MPT1327:FILL:DATA 3,’BCAST 2,#H4901,0,0’
The signaling commands from such strings are assembled into 48-bit address and
data codeword message values.
For an address codeword message, the timeslot (128-bits) consists of a 64-bit
control channel system codeword (CCSC), followed by the address message,
followed by a 16-bit parity word.
Data codeword messages are taken in pairs. Each has its own 16-bit parity word.
The firmware is never supplied with an odd number of codewords. The resulting
pair of 64-bit words is concatenated to again give 128-bits.
The resulting 128-bits are stored in the addressed location of the filler buffer.
Figure 101 on page 410, shows a signaling instruction being processed, and should
clarify this explanation.