Chapter 4
Configuration
MAN_905G_1.16
Page 54
Read/Write Mappings
The mappings can be “read” or “write” mappings. A Read mapping is a request sent to
another 905G to return a block of values. A Write mapping is a message sending a block of
values to another 905G. A Read mapping from 905G#2 to 905G#3 could be the same as a
Write mapping from 905G#3 to 905G#2 (that is, in the reverse direction) - except the Read
mapping is initiated from #2 and the Write mapping is initiated from #3.
Word/Bit Mappings
Read and Write mappings are also selected as Word or Bit mappings - that is, you can select
a Read Word mapping or a Read Bit mapping and you can select a Write Word mapping or a
Write Bit mapping. “Word” refers to a complete 16-bit register value; “Bit” refers to the
value of the most significant bit of a register - this bit is the “binary value” or “digital value”
of the register.
If you use a Word block mapping of 50 registers, you are transferring a block of 50 x 16-bit
values. If you use a Bit block mapping of 50 registers, you are only transferring the digital
value of each register - that is 50 x 1 bit values. This is a lot more efficient for a radio
message, but bit mappings are only suitable for discrete or digital I/O. A Bit mapping will
convert the 16-bit register to a single bit, transfer it and store the bit value in the most
significant bit of the destination register.
Note: The maximum block size for each block mapping is 64 registers.
REMOTE
905G
BLOCK OF I/O
REGISTERS
ACKNOWLEDGMENT
BLOCK WRITE
MESSAGE
BLOCK OF I/O
REGISTERS
READ REQUEST
BLOCK READ
MESSAGE
LOCAL
905G
