AP0100CS datasheet(52/73 Pages) ONSEMI

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AP0100CS HDR: Image Signal Processor (ISP)

Start-up Host Command Lock-out

AP0100CS/D Rev. 6, Pub. 1/16 EN

©Semiconductor Components Industries, LLC,2016.

Start-up Host Command Lock-out

The AP0100CS firmware implements an internal Host Command ‘lock’. At start-up, the

firmware obtains this lock, which prevents the Host from successfully issuing a host

command. All host commands will be rejected with EBUSY until the lock is freed.

The firmware releases the Host Command lock when it completes its start-up configura-

tion processing. The time to do this is dependent upon the configuration mechanism. It

is recommended that the Host poll the device with the System Manager Get State

command until ENOERR is returned.

Once the host can send serial commands it should perform the following sequence.

1. POLL command_register[15] until it clears (This is called the doorbell bit).

2. Continuously issue the SYSMGR_GET_STATE command (0x8101) until the result sta-

tus is not EBUSY

Below is some pseudocode that a host could use to implement the above sequence:

def systemWaitReadyFollowingReset(numRetries=10):

"""API function: waits for the system to be ready following reset (or powerup)

- first wait for the doorbell bit to clear - this indicates that the device can

accept host commands.

- then wait until the system has completed its configuration phase; the system is

ready when the SYSMGR_GET_STATE command does not return EBUSY.

- note the time for the system to be ready is dependent upon the active system

configuration mode.

- numRetries is the number of retries before timing-out

- returns result status code

"""

# Wait for doorbell bit to clear (indicates device can receive host commands)

retries = numRetries

while (0 != retries):

if (reg.COMMAND_REGISTER.DOORBELL.uncached_value == 0): break

# ready to receive

commands

retries -= 1

if (0 == retries):

# device failed to respond in time

return printError(ResultStatus.EIO, 'systemWaitReadyFollowingReset failed (doorbell

failed to clear)')

# Wait for the System Manager to complete the System Configuration phase

retries = numRetries

while (0 != retries):

res, currentState = sysmgrGetState()

if (ResultStatus.ENOERR == res): break

# we're done

if (ResultStatus.EBUSY != res):

return printError(res, 'systemWaitReadyFollowingReset failed (sysmgrGetState

failed)')

retries -= 1

if (0 == retries):

# device failed to respond in time

return printError(ResultStatus.EAGAIN, 'systemWaitReadyFollowingReset failed (device

busy)')

return res

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