Power Supply Controller (Psc) - Intermec CK30 Service Manual

Power Supply Controller (PSC)

CK30 Handheld Computer Service Manual
The output, BATT_FAULT* then gates off the load enable lines through
gates U17, U25, and U26. Flip-flop U15 latches the state of
BATT_FAULT* so that these loads do not come back on again when
power is restored.
Battery State
OK
Critical or battery out
Critical or battery out
PIC processor U38 (the PSC, or Power Supply Controller) is used to
supervise the following low-level power management functions. These are
discussed in further detail later in this section.
• Reset control
• IO key suspend/resume control
• Battery voltage A/D
• Temperature A/D
• Suspend timeout "enforcement"
• Supercap charging
• Battery status LED control
• FPGA IO power control
The microcontroller is flash-based and can be reprogrammed in-system
through the Debug port (P1) behind the SD slot door (see "PSC PIC" on
page 96). While the CK30 is on, the PSC functions as a peripheral of the
power management code running on the PXA255, accepting commands
and returning data over the I2C bus.
PSC I2C Syntax
The I2C controller in the PXA255 is always the host; the PSC is always a
slave device at address 0x12. The following I2C bus protocol is used to
send commands to the PSC and read data back. All commands to the
PSC are 1 byte long. The PSC echoes back the command byte, followed
by a single data byte.
Host sends:
[Start] [Slave ADDR write]
[Start] [Slave ADDR read]
Where = ACK from PSC
[ack]
PSC responds:
[CMD1] [DATA1]
[ack] [ack]
[DATAn] )
[nak]
Chapter 4 — Theory of Operation
System State
Not important
Awake
Suspended
[CMD1] ([CMD2]
[ack] [ack]
[ack]
([CMD2] [DATA2]
[ack]
Device Power
Controlled by software
Controlled by software
Off
...[CMDn] )
[ack] [ack]
... [CMDn]
[ack] [ack]
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