Error code 61XX means you will receive your data after calling Get Response command with Le=XX:
Example:
--> 00 A4 04 00 08 44 44 44 44 44 44 44 44
<-- 61 37
--> 00 C0 00 00 37
<-- some data of length 0x37 and status code 90 00.
Related question:
About Get Response command in javacard
Docs by Oracle:
There may be several APDU connections open at the same time using
different logical channels with the same card. However, since APDU
protocol is synchronous, there can be no interleaving of command and
their response APDUs across logical channels. Between the receipt of
the command APDU and the sending of the response APDU to that command,
only one logical channel is active. For T=0 protocol, for case 4 and
case 2 command APDUs the card may respond with '61 XX' or '6C XX'.
These special cases MUST be handled by the implementation in the
following manner:
'61 XX': The implementation MUST send GET RESPONSE to the card to get the response data before any other command is sent.
'6C XX': The implementation MUST resend the command after setting Le equal to XX received from the card before any other command is
sent.
In both the cases discussed above, the implementation MUST make sure
that between sending the command APDU, receiving status word '61 XX'
or '6C XX', and sending GET RESPONSE or resending the command APDU
with Le set to XX respectively, there MUST not be any other APDU
exchange on any logical channel with the card. In case the status word
'61 XX' is received multiple times successively from the card, the
implementation must accumulate all the response data received from the
card before returning it to the J2ME application. J2ME applications
MUST remain oblivious of the exchanges mentioned above and should only
get the response received as a result of the above operations.
