IP-POSPHY4 Altera, IP-POSPHY4 Datasheet - Page 30

• Manufacturer Part Number: IP-POSPHY4
• Description: IP CORE - POS-PHY Level 4 SPI 4.2 Interface
• Manufacturer: Altera
• Type: MegaCorer

Specifications of IP-POSPHY4

• Software Application: IP CORE, Interface And Protocols, COMMUNICATION
• Supported Families: Arria GX, Cyclone, HardCopy, Stratix
• Core Architecture: FPGA
• Core Sub-architecture: Arria, Cyclone, Stratix
• Rohs Compliant: NA
• Function: POS-PHY Level 4 Interface, Link-Layer/PHY Layer
• License: Initial License
• Lead Free Status / RoHS Status: na
• Lead Free Status / RoHS Status: na

3–8
POS-PHY Level 4 MegaCore Function User Guide
Receiver Options
f
1
1
If you turn on Ignore backpressure (only available when you turn on Shared buffer
with embedded addressing), the MegaCore function ignores the backpressure from
the receiver and simply sends data whenever the buffer is not empty. The MegaCore
function stops reading from the buffer only when the status framer is out of
synchronization, when a training pattern is inserted, or when there is not enough data
to complete a burst. The user logic is responsible for using the status outputs from the
MegaCore function to schedule data writes into the buffer appropriately.
If you turn off Ignore backpressure, a simple scheduling algorithm is employed. If
the status received for any port is satisfied, the transmitter stops reading from the
buffer on the next EOP or burst unit size boundary. If all ports are hungry or starving,
the transmitter sends the data in the buffer. So a satisfied status received for one port
prevents transmission for any port, leading to head-of-line blocking.
If you turn on Switch on end-of-packet, the scheduler stops sending from the current
port, and switches ports at the end of burst (that is, when the credits have all been
consumed), as well as when an EOP is sent. If you turn off Switch on end-of-packet,
the scheduler switches ports at the end of the burst (also includes switching when the
buffer is empty).
This option applies only to the individual buffers mode, and allows you to
parameterize the port switching capabilities of the transmit scheduler.
For more information, refer to
page
Turn on Burst Limit Enable, if you want the transmitter to limit the maximum size of
bursts it sends. Set the maximum burst value with the Burst Limit option (on the
Protocol Parameters tab). At the end of a burst limit a control word is inserted.
If you turn off Ignore LVDS DPA locked after training, which is only available for
Stratix II devices, a loss of dpa_lvds_locked causes the MegaCore function to stop
processing data, sends framing, and there is data loss and the possibility of
MSOP/EOP errors. If you turn on Ignore LVDS DPA locked after training, a loss of
dpa_lvds_locked does not trigger stop and framing, and data continues to process
normally. You must monitor the DIP4 error signal to assess if the data is correct or not
and trigger a retrain or not.
For Stratix III and Stratix IV devices, the dpa_lvds_locked signal never goes low, so
the MegaCore function behaves as if you turned on Ignore LVDS DPA locked after
training.
If the signal stat_rd_lvds_lock goes low during operation (after training), the
MegaCore function assumes that the lock is lost due to external conditions such as
jitter. This signal goes low if the capture phase of the hardware DPA block changes by
two or more phases. The two phases correspond to a amount that is lower than the
accepted threshold for the SPI4.2 Specification. When the signal goes low, the
MegaCore function states it is out of synchronization and requests a new training
sequence.
5–3.
“Individual Buffers Transmit Scheduler (tx_sched)” on
December 2010 Altera Corporation
Chapter 3: Parameter Settings
Optional Features