CT2553 Datasheet, PDF (16/36 Pages) Aeroflex Circuit Technology – CT2553 / 2554 / 2555 / 2556 Advanced Integrated MUX (AIM) Hybrid FOR MIL-STD-1553

RTU OPERATION
The RTU mode is selected by resetting the
CT2553 and setting the appropriate bits in the
Configuration Register.
RTU MEMORY CONFIGURATION. The user
configures the memory by:
1. Writing the start address of the Descriptor
Stack into the Stack Pointer location and
2. Setting up the Look-Up Table as described
below.
If both map areas (A and B) are utilized, this
procedure must be performed for each area. Note
that the Stack Pointer and Look-Up Table
locations are fixed; Data Block(s) locations are
user-defined. Message blocks may be loaded
anywhere in the non-fixed areas of the shared
RAM. However, each data block may not cross a
256 word boundary (i.e., bit 8 of the starting
address of the message block must match bit 8 of
the address of the last word of the message
block). An example of a typical RTU Memory Map
is given in Table 4. Figure 19 shows the RTU
Initialization steps.
Table 4 – Typical RTU Memory Map
HEX ADDRESS
FUNCTION
0100
0101
0104
0105
0108-013F
0140-017F
01C0-01FF
0180-019F
01A0-01BF
0200-021F
•
•
0EE0-0EFF
0000-00FF
0F00-0FFF
Fixed Areas
Descriptor Stack Pointer A
Reserved
Descriptor Stack Pointer B
Reserved
Spare
Look-Up Table A
Look-Up Table B
User Defined Areas
Data Block 1
Data Block 2
Data Block 3
•
•
Data Block 107
Descriptor Stack A
Descriptor Stack B
RTU LOOK-UP TABLE. The RTU mode uses a
Look-Up Table in order to map the Data Blocks
based upon incoming 1553 Command Words.
The CT2553 uses the T/R and Subaddress fields
to address the Look-Up Table. Each Look-Up
Table (A and B) location contains a user-defined
Data Block Pointer to an associated Data Block
(See Figures 20 and 21).
Note: The Data Block and Stack Pointers are
maintained
internally
using
an
8-BIT-REGISTER for the HIGH BYTE and an
8-BIT COUNTER for the LOW BYTE; the high
byte remains constant (user value) while the low
byte will wrap around from FF(H) to 00(H). For
example: a current Pointer value of 10 FF(H)
will increment to 10 00(H) and not 11 00(H).
The first 32 words of the Look-Up Table are
reserved for Data Blocks associated with Receive
Commands (T/R bit = 0). The remaining 32 words
are reserved for Data Blocks associated with
Transmit Commands (T/R bit = 1).
Mode Commands with data are mapped in the
same manner as non-mode commands. A
Synchronize With Data command maps to the
first or thirty-second Table entry (depending upon
subaddress: all 0's or all 1's), while a Transmit
Vector Word command points to the thirty-third or
sixty-fourth entry.
START
ISSUE RESET COMMAND
INITIALIZE STACK POINTER
SET UP LOOK-UP TABLE(S)
DATA BLOCK ASSIGNMENTS
SET UP DATA BLOCKS
INITIALIZE INTERRUPT
MASK REGISTER
SET CONFIGURATION
REGISTER TO RTU MODE
START REGISTER
WAIT FOR 1553 COMMAND
Figure 19 – RTU Initialization
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SCDCT2553 REV B 8/6/99 Plainview NY [phone]