LAN8810 Datasheet, PDF (67/83 Pages) Microchip Technology – GMII 10/100/1000 Ethernet Transceiver

LAN8810/LAN8810I
5.5.3 POWER-ON HARDWARE RESET TIMING
Figure 5-3 illustrates the nRESET, configuration strap/pin, and CONFIG[3:0] timing requirements in relation to power-
on. A hardware reset (nRESET assertion) is required following power-up. For proper operation, nRESET must be
asserted for no less than t_rstia. The nRESET pin can be asserted at any time, but must not be deasserted before t_purstd
after all external power supplies have reached operational levels. In order for valid configuration strap values to be read
at power-up, the t_css and t_csh timing constraints must be followed. In order for CONFIG[3:0] values to be read at power-
up, the t_cs and t_ch timing constraints must be followed. Refer to Section 3.6.1, "Hardware Reset (nRESET)," on page 22
for additional information.
FIGURE 5-3:
HARDWARE RESET TIMING
All External
Vopp
Power Supplies
nRESET
t_purstv
t_purstd
t_rstid
Configuration
Straps
Configuration Strap
Pins Output Drive
CONFIG[3:0]
t_rstia
t_css
t_csh
t_otaa
t_odad
t_cs
t_ch
.
TABLE 5-12: HARDWARE RESET TIMING VALUES
Symbol
Description
Min
Typ
Max
Units
t_purstd
t_purstv
t_rstid
t_rstia
t_css
t_csh
t_otaa
t_odad
t_cs
t_ch
External power supplies at operational level to nRESET
25
deassertion
External power supplies at operational level to nRESET
0
valid
nRESET input deassertion time
10
nRESET input assertion time
100
Configuration strap pins setup to nRESET deassertion 200
Configuration strap pins hold after nRESET deassertion 10
Output tri-state after nRESET assertion
Output drive after deassertion
40
CONFIG[3:0] setup to nRESET deassertion
0
CONFIG[3:0] hold after nRESET deassertion
1
mS
nS
S
S
nS
nS
50
nS
800
nS
nS
uS
Note 1: Device configuration straps are latched as a result of nRESET assertion. Refer to Section 3.8.1.1, "Config-
uration Straps," on page 24 details. Configuration straps must only be pulled high or low and must not be
driven as inputs.
2: nRESET deassertion must be monotonic.
DS00001870B-page 67
 2009-2015 Microchip Technology Inc.