48SWTQFN-EP datasheet(73/103 Pages) MAXIM

73 / 103 page

MAX9288/MAX9290

3.12Gbps GMSL Deserializers

for Coax or STP Input and MIPI CSI-2 Output

www.maximintegrated.com

Maxim Integrated │ 73

High-Bandwidth Digital Content

Protection (HDCP)

Note: The explanation of HDCP operation in this data

sheet is provided as a guide for general understanding.

Implementation of HDCP in a product must meet the

requirements given in the HDCP System v1.3 Amendment

for GMSL, which is available from DCP.

HDCP has two main phases of operation, authentication

and the link integrity check. The µC starts authentica-

tion by writing to the START_AUTHENTICATION bit in

the GMSL serializer. The GMSL serializer generates a

64-bit random number. The host µC first reads the 64-bit

random number from the GMSL serializer and writes it

to the deserializer. The µC then reads the GMSL serial-

izer public key selection vector (AKSV) and writes it to

the deserializer. The µC then reads the deserializer KSV

(BKSV) and writes it to the GMSL serializer. The µC

begins checking BKSV against the revocation list. Using

the cipher, the GMSL serializer and deserializer calculate

a 16-bit response value, R0 and R0’, respectively. The

GMSL amendment for HDCP reduces the 100ms mini-

mum wait time allowed for the receiver to generate R0’

(specified in HDCP rev 1.3) to 128 pixel clock cycles in

the GMSL amendment.

There are two response-value comparison modes, internal

comparison and µC comparison. Set EN_INT_COMP = 1

to select internal comparison mode. Set EN_INT_COMP

= 0 to select µC comparison mode. In internal compari-

son mode, the µC reads the deserializer response R0’

and writes it to the GMSL serializer. The GMSL serializer

compares R0’ to its internally generated response value

R0, and sets R0_RI_MATCHED. In µC comparison mode,

the µC reads and compares the R0/R0’ values from the

GMSL serializer/deserializer.

During response-value generation and comparison, the

host µC checks for a valid BKSV (having 20 1s and 20

0s is also reported in BKSV_INVALID) and checks BKSV

against the revocation list. If BKSV is not on the list and

the response values match, the host authenticates the

link. If the response values do not match, the µC resam-

ples the response values (as described in HDCP rev 1.3,

Appendix C). If resampling fails, the µC restarts authen-

tication by setting the RESET_HDCP bit in the GMSL

serializer. If BKSV appears on the revocation list, the host

cannot transmit data that requires protection. The host

knows when the link is authenticated and decides when

to output data requiring protection. The µC performs a link

integrity check every 128 frames or every 2s ±0.5s. The

GMSL serializer/deserializer generate response values

every 128 frames. These values are compared internally

(internal comparison mode) or can be compared in the

host µC.

In addition, the GMSL serializer/deserializer provide

response values for the enhanced link verification.

Enhanced link verification is an optional method of link

verification for faster detection of loss-of-synchronization.

For this option, the GMSL serializer and deserializer

generate 8-bit enhanced link-verification response values

(PJ and PJ’) every 16 frames. The host must detect three

consecutive PJ/PJ’ mismatches before resampling.

Encryption Enable

The GMSL link transfers either encrypted or nonen-

crypted data. To encrypt data, the host µC sets the

encryption enable (ENCRYPTION_ENABLE) bit in both

the GMSL serializer and deserializer. The µC must set

ENCRYPTION_ENABLE in the same VSYNC cycle in

both the GMSL serializer and deserializer (no internal

VSYNC falling edges between the two writes). The same

timing applies when clearing ENCRYPTION_ENABLE to

disable encryption.

Note: ENCRYPTION_ENABLE enables/disables encryp-

tion on the GMSL irrespective of the content. To comply

with HDCP, the µC must not allow content requiring

encryption to cross the GMSL unencrypted.

The µC must complete the authentication process before

enabling encryption. In addition, encryption must be dis-

abled before starting a new authentication session.

Synchronization of Encryption

The video vertical sync (VSYNC) synchronizes the start

of encryption. Once encryption has started, the GMSL

generates a new encryption key for each frame and each

line, with the internal falling edge of VSYNC and HSYNC.

Rekeying is transparent to data and does not disrupt the

encryption of video or audio data.

Repeater Support

The GMSL serializer/deserializer include features to build

an HDCP repeater. An HDCP repeater receives and

decrypts HDCP content and then encrypts and transmits

on one or more downstream links. A repeater can also use

decrypted HDCP content (e.g., to display on a screen).

To support HDCP repeater-authentication protocol, the

deserializer has a REPEATER register bit. This register

bit must be set to 1 by a µC (most likely on the repeater

module). Both the GMSL serializer and deserializer use

SHA-1 hash-value calculation over the assembled KSV

lists. HDCP GMSL links support a maximum of 15 receiv-

ers (total number including the ones in repeater modules).

48SWTQFN-EP Datasheet(PDF) 73 Page - Maxim Integrated Products

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