7I76 32
REFERENCE INFORMATION
SSLBP
PROCESS DATA ELEMENT PACKING AND UNPACKING
Ultimately all process data is transferred to and from the host via the interface 0,1,2
registers.
The packing of outgoing process data elements into these interface registers and
unpacking of incoming process data elements from these interface registers is done in the
order of process data descriptors listed in the PTOC. Process data elements in PTOC
order and process descriptor DATA_SIZE are packed into or unpacked from the interface
registers from LSB to MSB and from interface register 0 through interface register 2.
Read data and bidirectional data is unpacked from the interface registers read by
the host. Write data and bidirectional data is packed into the interface registers written by
the host.
Before a DOIT command is written to start a data transfer cycle with the remote
device, the host must write its packed outgoing process data (OPD in table below) to the
interface registers. (The CS register not currently used for outgoing data/control so is not
written)
HOST WRITES OUTGOING INTERFACE REGISTERS BEFORE DOIT
CS REG
MODE
X
X
X
INTERFACE 0
OPD BYTE 3
OPD BYTE 2
OPD BYTE 1
OPD BYTE 0
INTERFACE 1
OPD BYTE 7
OPD BYTE 6
OPD BYTE 5
OPD BYTE 4
INTERFACE 2
OPD BYTE 11
OPD BYTE 10
OPD BYTE 9
OPD BYTE 8
