9. Reset and Initialization > Initialization
CPS-1848 User Manual
195
June 2, 2014
Formal Status
This document is confidential and is subject to an NDA.
Integrated Device Technology
e. Program other configuration settings such as cut-thru mode (CUT_THRU_EN), and per-port reset behavior
(PORT_RST_CTL) using the
5. If the port has a link partner, enable the port by clearing
.PORT_DIS and PORT_LOCKOUT.
6. Disable IDLE2 functions as described in
.
7. Reset the port(s) using the
Device Reset and Control Register
The CPS-1848’s ports will revert back to their default values after a port reset.
8. Configure the port width using
[PWIDTH_OVRD] if the required setting is different from the
intended configuration.
9. Enable the ports to receive and transmit packets by setting
[INPUT_PORT_EN and
OUTPUT_PORT_EN] to 1.
9.2.4
Computing Timeout Values
This section discusses two timeout periods:
•
– The default value for TIMEOUT must be changed because it is unsuitable for most
systems.
•
– The switch TTL function is disabled by default. If the TTL function is required for correct system
operation, the field’s default value must be changed.
9.2.4.1
Setting the
Each RapidIO device has a standard register that defines the response timeout for the physical level protocol, such as receipt
of a link response control symbol after sending a link request. In the CPS-1848, this standard register is known as the
, and must be set correctly to ensure low latency packet transfer during error conditions.
In compliance to the RapidIO Specification (Rev. 2.1), the
has a default timeout period of
5.9 seconds. This timeout period, however, is too long for most applications.
Since there is one counter per device, the timeout value set must be for worst-case latency for all link partners connected to
the CPS-1848. The latency for response control symbols varies with the implementation of the link partner and the link speed.
The formula for setting TIMEOUT in the
is as follows:
ROUNDUP (MAX (LPLatency [0:n-1]) / 352)
Where:
• There are “n” link partners
• LPLatency is the maximum latency, in nanoseconds, for the link partner to do the following:
— Return a Packet Accepted, Packet Not Accepted, or Retry control symbol in response to a packet
— Return a Link Request control symbol in response to a Packet Not Accepted or Stomp control symbol
— Return a Link Response control symbol in response to a request:
• MAX returns the largest of a list of values
• ROUNDUP computes the smallest integer that is larger than the parameter value
Typically, the TIMEOUT value should be less than 10 microseconds. However, some link partner implementations, particularly
FPGA implementations, can increase the TIMEOUT value beyond 10 microseconds.
