SNLS605C July 2018 – April 2024 DS90UB935-Q1
PRODUCTION DATA
The input on the DS90UB935-Q1 GPIO pins can be forwarded to compatible deserializers over the FPD-Link III interface. Up to four GPIOs are supported in the forward direction.
The timing for the forward channel GPIO is dependent on the number of GPIOs assigned at the serializer. When a single GPIO input from the DS90UB935-Q1 serializer is linked to a compatible deserializer GPIO output, the value is sampled at every forward channel transmit frame. Two linked GPIO are sampled every two forward channel frames, and three or four linked GPIO are sampled every five frames. The typical latency for the GPIO is approximately 225ns but varies with the length of the cable. As the information is spread over multiple frames, the jitter is typically increased on the order of the sampling period (number of forward channel frames). TI recommends that the user maintain a 4x oversampling ratio for linked GPIO throughput. For example, when operating in 4Gbps synchronous mode with REFCLK = 25MHz, the maximum recommended GPIO input frequency based on the number of GPIO linked over the forward channel is shown in Table 6-6.
NUMBER OF LINKED FORWARD CHANNEL GPIOs (FC_GPIO_EN) |
SAMPLING FREQUENCY (MHz) AT FPD-Link III LINE RATE = 4Gbps |
MAXIMUM RECOMMENDED FORWARD CHANNEL GPIO FREQUENCY (MHz) | TYPICAL LATENCY (ns) | TYPICAL JITTER (ns) |
---|---|---|---|---|
1 | 100 | 25 | 225 | 12 |
2 | 50 | 12.5 | 225 | 24 |
4 | 20 | 5 | 225 | 60 |