11.5.61 PLCA Transmit Opportunity Timer Register
| Name: | PLCA_TOTMR |
| Address: | 0xCA04 |
| Bit | 15 | 14 | 13 | 12 | 11 | 10 | 9 | 8 | |
| Access | RO | RO | RO | RO | RO | RO | RO | RO | |
| Reset | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 |
| Bit | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 | |
| TOTMR[7:0] | |||||||||
| Access | R/W | R/W | R/W | R/W | R/W | R/W | R/W | R/W | |
| Reset | 0 | 0 | 1 | 0 | 0 | 0 | 0 | 0 | |
Bits 7:0 – TOTMR[7:0] PLCA Transmit Opportunity Timer
Configures the PLCA Transmit Opportunity time allowed for each node to begin transmitting and capture the carrier sense for all nodes on the network. The time is represented in increments of 100 ns (i.e., 1 BT). This field defaults to 32 bit times (3.2 μs) according to the IEEE 802.3cg specification (Clause 30), and the OPEN Alliance 10BASE‑T1S PLCA Management Registers specification Version 1.2.
Important: This field must be
configured identically across all nodes on the multidrop mixing segment.
CAUTION: Improper
configuration of Transmit Opportunity timer may result in reduced network performance
or collisions. Determination of the optimal Transmit Opportunity time requires
knowledge of various delays of each of the vendor PHYs on the mixing segment and
various physical layer propagation delay. It is recommended to leave this field at
its default value unless a full evaluation of delays has been performed.
Note: Due to discrepancies in the default value for this register
between Version 1.0 of the OPEN Alliance register map specification for this field an
Clause 30 of the IEEE 802.3cg specification, it is recommended that this field always
be configured to the desired value for all Microchip and non-Microchip devices on the
network.