B. Clocking > P_CLK Programming
493
Tsi578 User Manual
June 6, 2016
Integrated Device Technology
www.idt.com
15. Release the MAC from reset
— Write offset 0x132c8 with 0x7FFF0002
B.2
P_CLK Programming
The Tsi578 recommends a P_CLK operating frequency of 100 MHz. However, the device also
supports P_CLK frequencies less than the recommended 100 MHz. The ability to support other
P_CLK frequencies gives the Tsi578 flexibility in both application support and design.
The following sections describe the effects on the Tsi578 when the input frequency of the P_CLK
source is decreased from the recommended 100 MHz operating frequency.
B.2.1
RapidIO Specifications Directly Affected by Changes in the P_CLK
Frequency
The following sections describe how changing the P_CLK frequency to below the recommended
100 MHz operation affect the counters and state machines in the Tsi578 that are defined in the
RapidIO
Interconnect Specification (Revision 1.3)
.
B.2.1.1
Port Link Time-out CSR
RapidIO Part 6: 1x/4x LP-Serial Physical Layer Specification Revision 1.3: Section
6.6.2.2 Port Link Time-out CSR (Block Offset 0x20)
The
RapidIO Interconnect Specification (Revision 1.3)
defines the Port Link Time-out CSR as follows:
The
port-link
time-out control register contains the time-out timer value for all ports on a device.
This time-out is for link events, such as sending a packet to receiving the corresponding
acknowledge and sending a link-request to receiving the corresponding link-response. The reset
value is the maximum time-out interval, and represents between three and six seconds.
IDT Implementation
The Tsi578 supports this timer in the RapidIO Switch Port Link Time Out Control CSR
.
Effects of
changing the P_CLK frequency are shown in the following formula:
•
Time-out = 32/F x TVAL
— F is P_CLK frequency in MHz
— TVAL is the 24-bit counter setting
–
Maximum TVAL decimal value of 16,777,215 (0xFFFFFF)
The minimum frequency supported by the P_CLK input is 25 MHz. Operation above
100 MHz or below 25 MHz is not tested or guaranteed.