CS5530A datasheet(50/259 Pages) AMD

50 / 259 page

AMD Geode™ CS5530A Companion Device Data Book

Processor Interface

Revision 1.1

Figure 4-3. PIXEL Signal Connections

4.1.2

PSERIAL Pin Interface

The majority of the system power management logic is

implemented in the CS5530A, but a minimal amount of

logic is contained within the GX1 processor to provide

information that is not externally visible (e.g., graphics con-

troller).

The processor implements a simple serial communications

mechanism to transmit the CPU status to the CS5530A.

The processor accumulates CPU events in an 8-bit register

(defined in Table 4-1) which it transmits serially every 1 to

10 µs.

The packet transmitter holds the serial output pin (PSE-

RIAL) low until the transmission interval timer has elapsed.

Once the timer has elapsed, the PSERIAL pin is held high

for two clocks to indicate the start of packet transmission.

The contents of the Serial Packet Register are then shifted

out starting from bit 7 down to bit 0. The PSERIAL pin is

held high for one clock to indicate the end of packet trans-

mission and then remains low until the next transmission

interval. After the packet transmission is complete, the pro-

cessor’s Serial Packet Register’s contents are cleared.

The processor’s input clock is used as the clock reference

for the serial packet transmitter.

Once a bit in the register is set, it remains set until the com-

pletion of the next packet transmission. Successive events

of the same type that occur between packet transmissions

are ignored. Multiple unique events between packet trans-

missions accumulate in this register. The processor trans-

mits the contents of the serial packet only when a bit in the

Serial Packet Register is set and the interval timer has

elapsed.

For more information on the Serial Packet Register refer-

enced in Table 4-1, refer to the AMD Geode™ GX1 Proces-

sor Data Book.

The CS5530A decodes the serial packet after each trans-

mission and performs the power management tasks

CS5530A Datasheet(PDF) 50 Page - Advanced Micro Devices