Chapter 4 — Theory of Operation
PXA255 GPIO Signal Descriptions (continued)
PXA255 GPIO Function Signal Description Usage
GP32 -SDMMC_WP SD slot write protect 0 = write protect
1 = writes enabled
GP38 -HCR_OE HCR registers output enable. This signal floats high on cold
boot so that HCR register outputs float to their default-off states
(through pull-up and pull-down resistors). Once software has
initialized the HCR registers, software should enable the HCR
outputs by setting this bit low.
0 = HCR regs
low-Z
1 = HCR regs
high-Z
GP48 -POE/PCI_IRQ Mini PCI IRQ (CF slot OE if CF slot installed). PCI bridge
interrupts, PCI card interrupts and keypad interrupts all share
this line.
↓ = interrupt
GP66 KEY_DRV0 Keypad matrix column drive 0 0 = scan column
1 = idle
GP67 KEY_DRV1 Keypad matrix column drive 1 0 = scan column
1 = idle
GP68 KEY_DRV2 Keypad matrix column drive 2 0 = scan column
1 = idle
GP69 KEY_DRV3 Keypad matrix column drive 3 0 = scan column
1 = idle
GP70 KEY_DRV4 Keypad matrix column drive 4 0 = scan column
1 = idle
GP71 KEY_DRV5 Keypad matrix column drive 5 0 = scan column
1 = idle
GP72 KEY_DRV6 Keypad matrix column drive 6 0 = scan column
1 = idle
GP73 KEY_DRV7 Keypad matrix column drive 7 0 = scan column
1 = idle
GP79 PCI_SPARE Spare I/O from FPGA. May be used as an interrupt, GPIO, or
additional chip select to the FPGA.
GP80 -SD_PWR_EN Power enable for SD slot 0 = SD power on
1 = SD power off
HCR Output Signal Descriptions
HCR Bit Function Signal Description Usage
U16 16 BT_PWR_EN* Bluetooth module power enable 0 = on
1 = off
U16
17 BLUE_LED Blue System Light control
(moved from 0x1400_0000 bit 15)
0 = LED off
1 = LED on
U16 18 AUDIO_EN Audio power supply enable 0 = off
1 = on
U16
19 RESUME_EN
Resume Enable for non-I/O-key sources. This enables and
disables system resume from the following events:
- Tethered scanner trigger on 10-pin port (SCAN_TRIG)
- Tethered scanner trigger on 26-pin port (DOCK_TRIG)
- Dock serial DCD
- USB host present
Note that SCAN_PWR_EN must be asserted for SCAN_TRIG
to wake the system through this mechanism. Similarly,
DOCK_EN must be asserted for DOCK_TRIG to wake the
system. Dock DCD and USB need no other enable.
0 = disable resume
1 = enable resume
CK30 Handheld Computer Service Manual 45
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