The System Management Controller (SMC) is an 8051/8052 core inside the Southbridge. It manages the power sequencing, and is always active when the Xbox 360 has (standby or full) power applied. It controls the frontpanel, has a Realtime clock, decodes IR, manages temperatures, fans, DVDROM tray and a bunch of other things. It talks with the frontpanel board to set the LEDs. When the system is running, the kernel can communicate with the SMC, for example to query the realtime clock, open the dvd-tray etc.
Communication between kernel and SMC happens over a bidirectional FIFO (at ea001080 / ea001090). All messages and replies are 16 byte long and have the command id in the first byte.
void smc_send(void *msg)
{
while (!(readl(0xea001084) & 4)) // wait for FIFO ready
cpu_relax();
writel(4, 0xea001084); // start message
writesl(0xea001080, msg, 4); // send 16 bytes
writel(0, 0xea001084); // end message
}
</code>
Some messages have replies, which will be returned as 16 byte sequence similar to the message (they also have the command id in the first byte).
int smc_read_reply(void *msg)
{
if (!(readl(0xea001094) & 4)) // do we have a reply?
return 0;
writel(4, 0xea001094); // start reply
readsl(0xea001090, msg, 4); // read 16 bytes
writel(0, 0xea001094); // end reply
return 1;
}
</code>
| ID | Len | Example | Purpose |
|---|---|---|---|
| [[SMC_Command_0x82 | 0x82]] | 2-3 | ”\x82\0x04\0x31\0\0\0\0\0\0\0\0\0\0\0\0\0” |
| [[SMC_Command_0x8c | 0x8c]] | 3 | ”\x8c\0x01\0x00\0\0\0\0\0\0\0\0\0\0\0\0\0” |
| ID | Len | Example Query | Example Reply | Purpose |
|---|---|---|---|---|
| [[SMC_Command_0x01 | 0x01]] | 1:6 | ”\x01\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0” | 01 12 00 00 00 00 |
| [[SMC_Command_0x04 | 0x04]] | 1:11 | ”\x04\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0” | 04 602f 212223 01 00000000 |
| [[SMC_Command_0x07 | 0x07]] | 1:10 | ”\x07\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0” | 07ff 241b 2fa4 2cfa 262c |
| [[SMC_Command_0x0a | 0x0a]] | 1:2 | ”\x0a\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0” | 0a 60 |
| [[SMC_Command_0x0f | 0x0f]] | 1:2 | ”\x0f\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0” | 0f 54 |
| [[SMC_Command_0x11 | 0x11]] | 6:2 | ”\x11\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0” | 11 02 |
| [[SMC_Command_0x12 | 0x12]] | 1:6 | ”\x12\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0” | 1241 0203 0000 |
| [[SMC_Command_0x16 | 0x16]] | 1:2 | ”\x16\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0” | 16 0f |
| [[SMC_Command_0x17 | 0x17]] | 1:2 | ”\x17\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0” | 17 00 |
| ID | Len | Example Message | Purpose |
|---|---|---|---|
| [[SMC_Command_0x83 | 0x83]] | 2 | 83 64 |