
SMSC DS – FDC37N958FR
Page 146
Rev. 09/01/99
Output Enable Register
N/A
0x7F3E
VCC1
00000X10b
on VCC1 POR
00000X1Xb
on VCC2 POR
Host
8051
Power
Default
Output Enable Register VCC1 POR = 0x00000X10, VCC2 POR = 00000X1
X
b where
X
means the bit
holds its setting preceding VCC2 POR.
D7-D4
R/W
Reserved
0
D3
R/W
D2
R
D1
R/W
D0
R/W
8051 AR
iRESET_
OVRD
Power_Good
iRESET_OUT
32KHz Output
AR= Access Rights
IRESET_OUT
When
controlled by the 8051.
When
POWERGOOD=0,
forced high (within 100nsec) and latched. The
RESET_OUT pin is not driven until VCC2 is
applied. IRESET_OUT cannot be cleared by the
8051 until POWERGOOD=1.
POWERGOOD=1,
IRESET_OUT
is
IRESET_OUT
is
IRESET_OVRD
iRESET
iRESET_OUT bit functions as described above.
When set, iRESET_OUT is given direct control
over the internal reset and perhaps the
RESET_OUT and nRESET_OUT pins without
requiring the STOP_CLK counter or affecting the
8051STP_CLK bit or the HMEM register. In the
override mode, setting iRESET_OUT may or
may not drive RESET_OUT high and clearing
iRESET_OUT
may
RESET_OUT low.
Override
-
when
cleared
the
or
may
not
drive
The RESET_OUT Override function allows the
8051 to take the rest of the FDC37N958FR chip
(SIO) out of reset without giving up control (i.e.,
without stopping its clock and giving the flash
interface to the Host).
On the current FDC37N958FR, RESET_OUT is
driven low by this sequence of events.
1)
Sets STP_CNT to a non-zero value
2)
Clears iRESET_OUT bit, causing.
a) 8051STP_CLK bit 0 to get
set.
b) HMEM[7:0] to get set to
0x03
c) and STOP Counter to
start decrementing
3)
When STP_CNT reaches 0 the
RESET_OUT pin deasserts (goes
low) at which point the 8051’s clock
stops and the Host owns the Flash
Interface.
In addition to the above sequence, the
FDC37N958FR provides a means for the 8051
to directly control the state of the Super I/O
block’s internal reset. The FDC37N958FR
provides a means for the 8051 to drive low or
toggle the chip’s internal reset without stopping
the 8051 clock or giving the Flash interface to
the host.