System Control Registers
420
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
System Control
4.2.158 PCEPHY Register (Offset = 0x930) [reset = 0x0]
Ethernet PHY Power Control (PCEPHY)
The PCEPHY register controls the power applied to the EEPROM module. The function of this bit
depends on the current state of the device (run, sleep or deep-sleep mode) and value of the
corresponding bits in the RCGCEPHY, SCGCEPHY, and DCGCEPHY registers. If the Rn, Sn, or Dn bit of
the respective RCGCEPHY, SCGCEPHY, and DCGCEPHY registers is 1 and the device is in that mode,
the module is powered and receives a clock regardless of what the corresponding Pn bit in the PCEPHY
register is.
However, if the Rn, Sn, or Dn bit of the respective RCGCEPHY, SCGCEPHY, and DCGCEPHY registers
is 0 and the device is in that mode, then the module behaves differently depending on the value of the
corresponding Pn bit in the PCEPHY register. In this case, when the Pn bit is clear, the module is not
powered and does not receive a clock. If the Pn bit is set, the module is powered but does not receive a
clock.
lists the differences.
Table 4-181. Module Power Control
Rn, Sn, or Dn
Value in
Respective
RCGCx,
SCGCx, or
DCGCx
Register
Pn
Description
0
0
Module is not powered and does not receive a clock. In this case, the state of the peripheral
is not retained.
This is the lowest power consumption state of any peripheral, because it consumes no
dynamic nor leakage current. Hardware should perform a peripheral reset if the active mode
changes and the RCGCx, SCGCx, or DCGCx register is 1 or the P0 bit is changed to 1.
Software must reinitialize the peripheral when reenabled due to the loss of state.
0
1
Module is powered but does not receive a clock.
In this case, the peripheral is inactive. This is the second-lowest power consumption of any
peripheral, because it consumes only leakage current.
1
X
Module is powered and receives a clock.
NOTE:
The Ethernet PHY module is not powered up at reset to prevent an automatic negotiation on
power-up. To properly initialize the PHY, first inhibit the PHY from running on power up by
setting the PHYHOLD bit in the Ethernet Peripheral Configuration (EMACPC) register and
then set the P0 bit in the PCEPHY register. Once it is determined that the PHY is ready (by
polling the R0 bit in the Peripheral Ready (PREPHY) register), the PHY can be programmed
with its appropriate values.
NOTE:
If the MOSC is chosen as the clock to the Ethernet PHY then software must enable the
MOSC before enabling the Ethernet PHY by setting the P0 bit in the PCEPHY.
PCEPHY is shown in
and described in
Return to
Figure 4-164. PCEPHY Register
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
RESERVED
R-0x0
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
RESERVED
P0
R-0x0
R/W-
0x0