Altera Cyclone V Device Handbook page 695

cv_54011
2013.12.30
The command index is not checked for a 136-bit response or if the check_response_crc bit in the
cmd register is set to 0. For a 136-bit response and reserved CRC 48-bit responses, the command index is
reserved, that is, 0b111111.
Related Information
www.sdcard.org
For more information about response values, refer to Physical Layer Simplified Specification, Version 3.01
as described on the SD Association website.
Driving P-bit to the CMD Pin
The command path drives a one-cycle pull-up bit (P-bit) to 1 on the CMD pin between two commands if a
response is not expected. If a response is expected, the P-bit is driven after the response is received and before
the start of the next command. While accessing a CE-ATA card device, for commands that expect a CCS,
the P-bit is driven after the response only if the interrupts are disabled in the CE-ATA card (the nIEN bit
is set to 1 in the ATA control register), that is, the CCS expected bit (ccs_expected) in the cmd register
is set to 0. If the command expects the CCS, the P-bit is driven only after receiving the CCS.
Polling the CCS
CE-ATA card devices generate the CCS to notify the host controller of the normal ATA command completion
or ATA command termination. After receiving the response from the card, the command path state machine
performs the functions illustrated in the following figure according to cmd register bit values.
Figure 11-7: CE-ATA Command Path State Machine
The above figure illustrates:
• Response end bit state The state machine receives the end bit of the response from the card device. If
the ccs_expected bit of the cmd register is set to 1, the state machine enters the wait CCS state.
• Wait CCS The state machine waits for the CCS from the CE-ATA card device. While waiting for the
CCS, the following events can happen:
1. Software sets the send CCSD bit (send_ccsd) in the ctrl register, indicating not to wait for CCS
and to send the CCSD pattern on the command line.
2. Receive the CCS on the CMD line.
• Send CCSD command Sends the CCSD pattern (0b00001) on the CMD line.
SD/MMC Controller
Send Feedback
†
ccs_expected = 1
cmd_in = 0
wait_CCS
okay_to_send_ccsd
counter_zero
send_CCSD
†
Response Transmit
End Bit CMD12
ccs_expected = 0
Command
wait_tncc
Idle
†
†
†
Driving P-bit to the CMD Pin
†
†
send_auto_stop_ccsd
†
Altera Corporation
11-17
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