SPI Programming Manual (G06.24+, H06.03+, J06.03+)

SPI Concepts and Protocol
SPI Programming Manual—427506-006
2-14
Message Header
The SPI procedure SSINIT initializes an SPI buffer and places values in header
tokens. SSPUT puts tokens into a buffer, and SSGET retrieves token values from a
buffer. Section 3, The SPI Procedures
, describes the SPI procedures.
All modifications of an SPI buffer must be performed using the SPI procedures. SPI
buffers contain many specialized data structures and can be corrupted if manipulated
in any other way.
Message Header
The two types of SPI messages are: messages containing commands or responses,
and messages reporting events. A header token in each SPI message specifies
whether the message is a command/response message or an event message. This
manual describes command/response messages. For information about event
messages and the event message header, see the
EMS Manual .
The header portion of a command/response buffer contains:
•
A header type indicating a command/response message
•
The length of the message buffer
Figure 2-3. The SPI Buffer
VST007.vsd
Message Header
H
Legend
An SPI buffer or message
H The SPI message header
T
n A token with ID number n
Message Body
Used Length
Buffer Length
Tokens
H T1 T2 T2 T8
VST007.vsd
Message Header
H
Legend
An SPI buffer or message
H The SPI message header
T
n A token with ID number n
Message Body
Used Length
Buffer Length
Tokens
H T1 T2 T2 T8