MEN G25A, Руководство пользователя

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Hardware/Software Interface
20G025A00 E3

2017-04-20 Page 62
5.4 BMC API (Application Programming Interface)
The G25A uses a generic command interface for communication between the CPU (host)
and the BMC. Application software uses command packets to communicate with the BMC.
The application software controls the BMC via I2C/SMBus. The device address is
0x4D
(in
7-bit, non-shifted notation) or
0x9A
/
0x9B
(in 8-bit, shifted notation, write/read).
5.4.1 BMC Command Packets
5.4.1.1 Command Packet Protocol
From a logical point of view, the command protocol has the following characteristics:

Commands are always initiated by the host. The BMC never sends packets without
the host requesting it to do so.

Packets are either
- unidirectional from host to BMC, without an answer from the BMC
- bidirectional, with an answer from the BMC

Each command has a unique identifier, consisting of the command opcode and a
packet type:
Table 36. BMC API – Packet types
Packet Type Description
Request Data
Host > BMC
Response Data
BMC > Host
Error Signaling
PT_SB Send command only None No response -
PT_RBD Send command, get one data byte
from BMC
None 1 byte Response byte =
0xFF
PT_WBD Send command, send one data
byte to BMC
1 byte No response -
PT_RWD Send command, get two data
bytes from BMC
None 2 bytes Response byte =
0xFFFF
PT_WWD Send command, send two data
bytes to BMC
2 bytes No response -