Difference between revisions of "PinePhone Power Management"
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Line 16: | Line 16: | ||
| 3.3V | | 3.3V | ||
| No | | No | ||
| No | | No (VCC-IO) | ||
| VCC-EFUSE, VCC-IO, VCC-PC (VQMMC2), VCC-PD, VCC-USB; Modem [I2C, PCM, UART], Motor, Pogo I2C, UART0, VMMC0, VMMC2, WiFi CHIP_EN | | VCC-EFUSE, VCC-IO, VCC-PC (VQMMC2), VCC-PD, VCC-USB; Modem [I2C, PCM, UART], Motor, Pogo I2C, UART0, VMMC0, VMMC2, WiFi CHIP_EN | ||
|- | |- | ||
Line 64: | Line 64: | ||
| 1.8V | | 1.8V | ||
| No | | No | ||
| No | | No (VCC-PL) | ||
| VCC-PL; Pogo INT | | VCC-PL; Pogo INT | ||
|- | |- | ||
Line 70: | Line 70: | ||
| 3.0V | | 3.0V | ||
| No | | No | ||
| No | | No (KEYADC) | ||
| AVCC, KEYADC, VCC-PLL | | AVCC, KEYADC, VCC-PLL | ||
|- | |- | ||
| DLDO1 | | DLDO1 | ||
| 3.3V | | 3.3V | ||
| No | | No | ||
| No (ANX7688 AVDD33) | |||
| HVCC, VCC-DSI; ANX7688 [AVDD33, HDMI_VT, I2C, ANX-V1.0 Enable, VCONN_EN Disable Pull-up], HDMI [DDC, HPD], Proximity LED, Sensor I2C, Sensor VDD | | HVCC, VCC-DSI; ANX7688 [AVDD33, HDMI_VT, I2C, ANX-V1.0 Enable, VCONN_EN Disable Pull-up], HDMI [DDC, HPD], Proximity LED, Sensor I2C, Sensor VDD | ||
|- | |- | ||
Line 128: | Line 128: | ||
|- | |- | ||
| GPIO0-LDO | | GPIO0-LDO | ||
| | | 3.3V | ||
| Yes | | Yes | ||
| Yes | | Yes | ||
| Backlight PWM, LCD, Proximity sensor, Touchscreen [I2C, VCC] | | Backlight PWM, LCD, Proximity sensor VDD, Touchscreen [I2C, VCC] | ||
|- | |- | ||
| GPIO1-LDO | | GPIO1-LDO | ||
| 1.8V | | 1.8V | ||
| No | |||
| No (ANX7688 DVDD1V8) | | No (ANX7688 DVDD1V8) | ||
| ANX7688 [AVDD1V8, DVDD1V8, CC, HDMI DDC, I2C, Power/Reset pull-up] | | ANX7688 [AVDD1V8, DVDD1V8, CC, HDMI DDC, I2C, Power/Reset pull-up] | ||
|- | |- | ||
Line 176: | Line 176: | ||
|} | |} | ||
=== Suggested Hardware Changes === | === Suggested Regulator Hardware Changes === | ||
==== ANX7688 ==== | ==== ANX7688 ==== | ||
# Move ANX7688 AVDD33 (the chip input only, not the other things connected to 3v3) and ANX7688 I2C Level Shift (3.3V side) from DLD01 to DCDC1 | # Move ANX7688 AVDD33 (the chip input only, not the other things connected to 3v3) and ANX7688 I2C Level Shift (3.3V side) from DLD01 to DCDC1, and ANX7688 VCONN_EN Disable Pull-up (R1355 and R1366) from DLDO1 to ANX1.8V | ||
# Move ANX7688 | # <strike>Move ANX7688 ANX1.8V from GPIO1-LDO to ALDO2</strike> | ||
# Move ANX7688 ANX-V1.0 Regulator Enable | # Move ANX7688 ANX-V1.0 Regulator Enable (R1352) from DLDO1 to a GPIO | ||
These are all medium priority. | |||
The result of these changes would be that: | The result of these changes would be that: | ||
# The always-on part of the ANX7688 chip will always be powered | # The always-on part of the ANX7688 chip (AVDD33, DVDD1V8) will always be powered | ||
# GPIO1-LDO only needs to be powered when a USB cable is detected, and is enough to power the rest of the chip (except HDMI) | # GPIO1-LDO only needs to be powered when a USB cable is detected, and is enough to power the rest of the chip (except HDMI) | ||
# DLDO1 only needs to be enabled if the display pipeline or sensors are active, even if a USB cable is plugged in | # DLDO1 only needs to be enabled if the display pipeline or sensors are active, even if a USB cable is plugged in | ||
==== Assignments after Suggested Changes | <!--==== Sensors ==== | ||
# This may or may not be a good idea, so it's a very weak suggestion: Swap the VDD and LEDA inputs of the STK3311-A sensor, moving VDD to DLDO1 and LEDA to GPIO0-LDO. The sensor VDD needs to match the I2C voltage, and the LED driver should be on a separate power supply from the sensors. There is some concern, because GPIO0-LDO has a 100mA limit, but the proximity sensor should work properly at the lowest LED drive current (12.5mA). | |||
--> | |||
=== Assignments after Suggested Changes === | |||
Note: Only regulators that were modified are included here. | Note: Only regulators that were modified are included here. | ||
Line 204: | Line 211: | ||
| 3.3V | | 3.3V | ||
| No | | No | ||
| No | | No (VCC-IO) | ||
| VCC-EFUSE, VCC-IO, VCC-PC (VQMMC2), VCC-PD, VCC-USB; ANX7688 [AVDD33, I2C], Modem [I2C, PCM, UART], Motor, Pogo I2C, UART0, VMMC0, VMMC2, WiFi CHIP_EN | | VCC-EFUSE, VCC-IO, VCC-PC (VQMMC2), VCC-PD, VCC-USB; ANX7688 [AVDD33, I2C], Modem [I2C, PCM, UART], Motor, Pogo I2C, UART0, VMMC0, VMMC2, WiFi CHIP_EN | ||
|- | |- | ||
Line 210: | Line 217: | ||
| 1.8V | | 1.8V | ||
| No | | No | ||
| No | | No (VCC-PL) | ||
| VCC-PL; ANX7688 [DVDD1V8], Pogo INT | | VCC-PL; ANX7688 [DVDD1V8], Pogo INT | ||
|- | |- | ||
Line 217: | Line 224: | ||
| Yes | | Yes | ||
| Yes | | Yes | ||
| HVCC, VCC-DSI; ANX7688 [HDMI_VT], HDMI [DDC, HPD], Proximity | | HVCC, VCC-DSI; ANX7688 [HDMI_VT], HDMI [DDC, HPD], Proximity sensor VDD, Sensor I2C, Sensor VDD | ||
|- | |||
| GPIO0-LDO | |||
| 3.3V | |||
| Yes | |||
| Yes | |||
| Backlight PWM, LCD, Proximity LED, Touchscreen [I2C, VCC] | |||
|- | |- | ||
| GPIO1-LDO | | GPIO1-LDO | ||
Line 228: | Line 241: | ||
=== Open Questions === | === Open Questions === | ||
* How is ANX1.8V actually powered? from GPIO1-LDO or PS or both? | * How is ANX1.8V actually powered? from GPIO1-LDO (R1309) or PS (U1301) or both? | ||
* Is DLDO2 supposed to be 1.8V or 3.3V? The schematic says both in different places. | * Is DLDO2 supposed to be 1.8V or 3.3V? The schematic says both in different places. | ||
** From LCD and LCD controller datasheets, this should be 1.8V. | |||
* If DLDO2 is 3.3V, can we spread the HDMI/DSI/Sensors better across DLDO1 and DLDO2 so they can be more independent? | * If DLDO2 is 3.3V, can we spread the HDMI/DSI/Sensors better across DLDO1 and DLDO2 so they can be more independent? | ||
** Looks like this is N/A, because DLDO2 should be 1.8V. | |||
* | |||
* | |||
== GPIO == | == GPIO == | ||
Line 254: | Line 252: | ||
Note: only pins relevant to power management are included in this table. | Note: only pins relevant to power management are included in this table. | ||
{| class="wikitable" | |||
|- | |||
! Pin | |||
! Signal Name | |||
! Description | |||
! Direction (as modem) | |||
! Needed in suspend? | |||
! Connected to | |||
|- | |||
| 1 | |||
| <tt>WAKEUP_IN</tt> | |||
| Drive low to wake up the modem | |||
| I | |||
| No | |||
| PH7 (active high) | |||
|- | |||
| 2 | |||
| <tt>AP_READY</tt> | |||
| Drive high/low to signal the A64 is ready to receive URCs | |||
| I | |||
| No (if held) | |||
| NC | |||
|- | |||
| 4 | |||
| <tt>W_DISABLE#</tt> | |||
| Drive low to enter Airplane Mode | |||
| I | |||
| No (if held/tristate) | |||
| PH8 (active high) | |||
|- | |||
| 20 | |||
| <tt>RESET_N</tt> | |||
| Drive low to reset the modem | |||
| I | |||
| No (if held/tristate) | |||
| PC4 (active high) | |||
|- | |||
| 21 | |||
| <tt>PWRKEY</tt> | |||
| Drive low to turn the modem on/off | |||
| I | |||
| No (if held/tristate) | |||
| PB3 (active high) | |||
|- | |||
| 61 | |||
| <tt>STATUS</tt> | |||
| Open drain output, pulled low when the modem is on | |||
| O | |||
| No | |||
| PB3 | |||
|- | |||
| 62 | |||
| <tt>RI</tt> | |||
| Pulled low to request host wakeup | |||
| O | |||
| Yes | |||
| PB2 | |||
|- | |||
| 66 | |||
| <tt>DTR</tt> | |||
| Drive low to wake up the modem | |||
| I | |||
| No | |||
| PL6 (active low) | |||
|} | |||
=== Current Port L Pin Assignments === | === Current Port L Pin Assignments === | ||
Line 348: | Line 412: | ||
=== Pins Active During Suspend === | === Pins Active During Suspend === | ||
=== Suggested Hardware Changes === | === Suggested GPIO Hardware Changes === | ||
# Connect <tt>WL-REG-ON</tt> (PL2) to <tt>WL-PMU-EN</tt> (WiFi). ''bugfix'' | |||
# Connect the LIS3MDL <tt>DRDY</tt> pin, not <tt>INT</tt> pin, to PB1. ''bugfix'' | |||
# Reconnect <tt>LINEOUTN</tt> to make the line output differential. | |||
# Connect PH7 to <tt>AP_READY</tt> instead of <tt>WAKEUP_IN</tt>. Since the A64 needs to drive this pin high (no pull-up on the modem side), this uses the level shifter channel previously used by RI (U1503 channel 4). | |||
# Swap <tt>DTR</tt> (was at PL6, now at PB2 with U1503 channel 3 level shift) and <tt>RI</tt> (was at PB2, now at PL6 with '''no level shift''', but a pull-up to ALDO2 on the A64 side*). ''partly a bugfix'' | |||
# Connect the modem <tt>PWRKEY</tt> to PB3 only, not <tt>STATUS</tt> or DCDC1 (depopulate R1526). ''bugfix'' | |||
# Connect the modem <tt>STATUS</tt> to PH9. This is an open-drain signal, so it needs a pull-up on the A64 side. ''bugfix'' | |||
# Disconnect the modem I2C. The level shifter can be repurposed for the next change (modem debug UART). | |||
# <strike>Connect the modem debug UART TX/RX to PD0-1.</strike> | |||
# <strike>Move the modem main UART TX/RX to PD2-3. Motor and CSI reset that are currently at PD2-3 would need to be moved elsewhere.</strike> | |||
# Connect both AXP803 <tt>USB-DRVVBUS</tt> (populate R1300) and ANX7688 <tt>VBUS_CTRL</tt> to <tt>DRVVBUS</tt> (in addition to PD6). | |||
## <strike>Connecting to ANX7688 <tt>VBUS_CTRL</tt> would need a level shift to 1.8V.</strike> | |||
## Alternatively, swap PL9 and PD6, so the level shift is not necessary, since PL9 is already a 1.8V logic level. | |||
## <strike>Alternatively, do not connect ANX7688 <tt>VBUS_CTRL</tt>, and at least populate R1300 to connect AXP803 <tt>USB-DRVVBUS</tt>.</strike> | |||
# Reorient the transistors for <tt>ANX_POWER</tt> (PD10) and <tt>ANX_RESET</tt> (PL9) so they do not invert their input, and (more importantly) produce a low-level output by default. (Since PL9 is already at 1.8V, it may no longer need a transistor.) | |||
# <strike>Remove the transistors inverting <tt>VCONN1_EN</tt> and <tt>VCONN2_EN</tt>, and use a pull-up to <tt>DVDD1V8</tt> (that is really already present) instead of the pull-up to <tt>3V3</tt>.</strike> | |||
'''Note:''' | |||
Changes 1-7 and 11 are high priority. | |||
Changes 12-13 are medium priority. | |||
Changes 8-10 are low priority. | |||
* There should be at least one pin where the default value at boot changes, due to being pulled differently, for use in distinguishing the hardware revisions. In v1.1, PL6 reads 0 at boot. Since RI is an active-low interrupt, it needs a pull up. And it doesn't need any level translation. So that's our perfect opportunity. If PL6 reads low at boot, it's a v1.1 device; if PL6 reads high at boot, it's a v1.2 device. | |||
=== Open Questions === | === Open Questions === | ||
* What exactly is the modem PWRKEY connected to? | * What exactly is the modem PWRKEY currently connected to? PB3? STATUS? DCDC1? | ||
* Currently STATUS pin is connected to PWRKEY and to PB3. STATUS can't be read reliably since voltage divider from R1526 and R1517 places the STATUS signal at 0V or 0.5*Vcc-IO, which is unspecified input value according to A64 datasheet (Vih is 0.7*Vcc-IO, Vil is 0.3*Vcc-IO, the range in between is unspecified). | |||
[[Category:PinePhone]] [[Category:Allwinner A64]] |
Latest revision as of 14:57, 26 April 2021
The data on this page is based on the the PinePhone v1.1 - Braveheart.
Regulators
Current Assignments
Name/GPIO | Output Voltage | Can disable at runtime? | Can disable in suspend? | Consumers (internal/external separated by semicolon) |
---|---|---|---|---|
DCDC1 | 3.3V | No | No (VCC-IO) | VCC-EFUSE, VCC-IO, VCC-PC (VQMMC2), VCC-PD, VCC-USB; Modem [I2C, PCM, UART], Motor, Pogo I2C, UART0, VMMC0, VMMC2, WiFi CHIP_EN |
DCDC2 | DVFS | No | Yes | VDD-CPUX |
DCDC3 | DVFS | N/A | N/A | VDD-CPUX (polyphase with DCDC2) |
DCDC4 | N/A | Yes | Yes | Not used |
DCDC5 | 1.2V | No | Yes (future) | VCC-DRAM; DRAM |
DCDC6 | 1.1V | No | Yes (future) | VDD-SYS |
DC1SW | N/A | Yes | Yes | Not used |
ALDO1 | 2.8V | Yes | Yes | VCC-PE; Camera AFVCC, Camera DOVDD, CSI I2C, Pogo I2C |
ALDO2 | 1.8V | No | No (VCC-PL) | VCC-PL; Pogo INT |
ALDO3 | 3.0V | No | No (KEYADC) | AVCC, KEYADC, VCC-PLL |
DLDO1 | 3.3V | No | No (ANX7688 AVDD33) | HVCC, VCC-DSI; ANX7688 [AVDD33, HDMI_VT, I2C, ANX-V1.0 Enable, VCONN_EN Disable Pull-up], HDMI [DDC, HPD], Proximity LED, Sensor I2C, Sensor VDD |
DLDO2 | 1.8V? 3.3V? | Yes | Yes | MIPI-DSI VIO |
DLDO3 | 2.8V | Yes | Yes | Camera AVDD |
DLDO4 | 1.8V-3.3V | Yes | Yes | VCC-PG; VQMMC1 |
ELDO1 | 1.8V | No | No (DRAM) | CPVDD; DRAM |
ELDO2 | N/A | Yes | Yes | Not used |
ELDO3 | 1.8V | Yes | Yes | Camera DVDD |
FLDO1 | 1.2V | Yes | Yes | HSIC-VCC (not used) |
FLDO2 | 1.1V | No | No (VDD-CPUS) | VDD-CPUS |
GPIO0-LDO | 3.3V | Yes | Yes | Backlight PWM, LCD, Proximity sensor VDD, Touchscreen [I2C, VCC] |
GPIO1-LDO | 1.8V | No | No (ANX7688 DVDD1V8) | ANX7688 [AVDD1V8, DVDD1V8, CC, HDMI DDC, I2C, Power/Reset pull-up] |
PD6 | 5.0V | Yes | Yes | USB OTG |
PD8 | 5.0V | Yes | Yes | Pogo supply, USB OTG via PD6 |
PD9 | 5.0V | Yes | Yes | VCONN (USB Type C) |
PH10 | PWM | Yes | Yes | Backlight |
PL7 | VBAT | Yes | Yes | Modem |
ANX-V1.0 | 1.0V | Yes | Yes | ANX7688 [AVDD1V0, DVDD1V0] |
Suggested Regulator Hardware Changes
ANX7688
- Move ANX7688 AVDD33 (the chip input only, not the other things connected to 3v3) and ANX7688 I2C Level Shift (3.3V side) from DLD01 to DCDC1, and ANX7688 VCONN_EN Disable Pull-up (R1355 and R1366) from DLDO1 to ANX1.8V
Move ANX7688 ANX1.8V from GPIO1-LDO to ALDO2- Move ANX7688 ANX-V1.0 Regulator Enable (R1352) from DLDO1 to a GPIO
These are all medium priority.
The result of these changes would be that:
- The always-on part of the ANX7688 chip (AVDD33, DVDD1V8) will always be powered
- GPIO1-LDO only needs to be powered when a USB cable is detected, and is enough to power the rest of the chip (except HDMI)
- DLDO1 only needs to be enabled if the display pipeline or sensors are active, even if a USB cable is plugged in
Assignments after Suggested Changes
Note: Only regulators that were modified are included here.
Name/GPIO | Output Voltage | Can disable at runtime? | Can disable in suspend? | Consumers (internal/external separated by semicolon) |
---|---|---|---|---|
DCDC1 | 3.3V | No | No (VCC-IO) | VCC-EFUSE, VCC-IO, VCC-PC (VQMMC2), VCC-PD, VCC-USB; ANX7688 [AVDD33, I2C], Modem [I2C, PCM, UART], Motor, Pogo I2C, UART0, VMMC0, VMMC2, WiFi CHIP_EN |
ALDO2 | 1.8V | No | No (VCC-PL) | VCC-PL; ANX7688 [DVDD1V8], Pogo INT |
DLDO1 | 3.3V | Yes | Yes | HVCC, VCC-DSI; ANX7688 [HDMI_VT], HDMI [DDC, HPD], Proximity sensor VDD, Sensor I2C, Sensor VDD |
GPIO0-LDO | 3.3V | Yes | Yes | Backlight PWM, LCD, Proximity LED, Touchscreen [I2C, VCC] |
GPIO1-LDO | 1.8V | Yes | Yes | ANX7688 [ANX-V1.0 Enable, AVDD1V8, CC, HDMI DDC, I2C, Power/Reset pull-up, VCONN_EN Disable Pull-up] |
Open Questions
- How is ANX1.8V actually powered? from GPIO1-LDO (R1309) or PS (U1301) or both?
- Is DLDO2 supposed to be 1.8V or 3.3V? The schematic says both in different places.
- From LCD and LCD controller datasheets, this should be 1.8V.
- If DLDO2 is 3.3V, can we spread the HDMI/DSI/Sensors better across DLDO1 and DLDO2 so they can be more independent?
- Looks like this is N/A, because DLDO2 should be 1.8V.
GPIO
Current Modem Pin Assignments
Note: only pins relevant to power management are included in this table.
Pin | Signal Name | Description | Direction (as modem) | Needed in suspend? | Connected to |
---|---|---|---|---|---|
1 | WAKEUP_IN | Drive low to wake up the modem | I | No | PH7 (active high) |
2 | AP_READY | Drive high/low to signal the A64 is ready to receive URCs | I | No (if held) | NC |
4 | W_DISABLE# | Drive low to enter Airplane Mode | I | No (if held/tristate) | PH8 (active high) |
20 | RESET_N | Drive low to reset the modem | I | No (if held/tristate) | PC4 (active high) |
21 | PWRKEY | Drive low to turn the modem on/off | I | No (if held/tristate) | PB3 (active high) |
61 | STATUS | Open drain output, pulled low when the modem is on | O | No | PB3 |
62 | RI | Pulled low to request host wakeup | O | Yes | PB2 |
66 | DTR | Drive low to wake up the modem | I | No | PL6 (active low) |
Current Port L Pin Assignments
Pin | Signal Name | Description | Direction | Needed in suspend? |
---|---|---|---|---|
PL0 | PMU-SCK | AXP803 I2C/RSB Clock | O | Yes |
PL1 | PMU-SDA | AXP803 I2C/RSB Data | I/O | Yes |
PL2 | WL-REG-ON | Not Connected | N/A | N/A |
PL3 | WL-WAKE-AP | Wake-on-WLAN Interrupt | I | Yes |
PL4 | BT-RST-N | Bluetooth Reset Control | O | No (if held) |
PL5 | BT-WAKE-AP | Wake-on-BT Interrupt | I | Yes |
PL6 | DTR | Modem DTR (Wakeup Request) | O | No |
PL7 | 4G-PWR-BAT | Modem Power Supply Control | O | No (if held) |
PL8 | ANX7688-CABLE_DET | ANX7688 Cable Detection Interrupt | I | Yes |
PL9 | ANX_RESET | ANX7688 Reset Control | O | No (if held) |
PL10 | LCD-PWM | LCD Backlight PWM Brightness Control | O | No |
PL11 | ANX7688-INT | ANX7688 Alert Interrupt | I | Yes |
PL12 | POGO-INT | Pogo Pin Interrupt | I | Yes |
Pins Held During Suspend
Pins Active During Suspend
Suggested GPIO Hardware Changes
- Connect WL-REG-ON (PL2) to WL-PMU-EN (WiFi). bugfix
- Connect the LIS3MDL DRDY pin, not INT pin, to PB1. bugfix
- Reconnect LINEOUTN to make the line output differential.
- Connect PH7 to AP_READY instead of WAKEUP_IN. Since the A64 needs to drive this pin high (no pull-up on the modem side), this uses the level shifter channel previously used by RI (U1503 channel 4).
- Swap DTR (was at PL6, now at PB2 with U1503 channel 3 level shift) and RI (was at PB2, now at PL6 with no level shift, but a pull-up to ALDO2 on the A64 side*). partly a bugfix
- Connect the modem PWRKEY to PB3 only, not STATUS or DCDC1 (depopulate R1526). bugfix
- Connect the modem STATUS to PH9. This is an open-drain signal, so it needs a pull-up on the A64 side. bugfix
- Disconnect the modem I2C. The level shifter can be repurposed for the next change (modem debug UART).
Connect the modem debug UART TX/RX to PD0-1.Move the modem main UART TX/RX to PD2-3. Motor and CSI reset that are currently at PD2-3 would need to be moved elsewhere.- Connect both AXP803 USB-DRVVBUS (populate R1300) and ANX7688 VBUS_CTRL to DRVVBUS (in addition to PD6).
Connecting to ANX7688 VBUS_CTRL would need a level shift to 1.8V.- Alternatively, swap PL9 and PD6, so the level shift is not necessary, since PL9 is already a 1.8V logic level.
Alternatively, do not connect ANX7688 VBUS_CTRL, and at least populate R1300 to connect AXP803 USB-DRVVBUS.
- Reorient the transistors for ANX_POWER (PD10) and ANX_RESET (PL9) so they do not invert their input, and (more importantly) produce a low-level output by default. (Since PL9 is already at 1.8V, it may no longer need a transistor.)
Remove the transistors inverting VCONN1_EN and VCONN2_EN, and use a pull-up to DVDD1V8 (that is really already present) instead of the pull-up to 3V3.
Note: Changes 1-7 and 11 are high priority. Changes 12-13 are medium priority. Changes 8-10 are low priority.
* There should be at least one pin where the default value at boot changes, due to being pulled differently, for use in distinguishing the hardware revisions. In v1.1, PL6 reads 0 at boot. Since RI is an active-low interrupt, it needs a pull up. And it doesn't need any level translation. So that's our perfect opportunity. If PL6 reads low at boot, it's a v1.1 device; if PL6 reads high at boot, it's a v1.2 device.
Open Questions
- What exactly is the modem PWRKEY currently connected to? PB3? STATUS? DCDC1?
- Currently STATUS pin is connected to PWRKEY and to PB3. STATUS can't be read reliably since voltage divider from R1526 and R1517 places the STATUS signal at 0V or 0.5*Vcc-IO, which is unspecified input value according to A64 datasheet (Vih is 0.7*Vcc-IO, Vil is 0.3*Vcc-IO, the range in between is unspecified).