8/01/00
Am79C976
217
P R E L I M I N A R Y
13-8
RES
Reserved locations. Written as
zeros and read as undefined.
7-0
EPADDRU
Expansion Port Address Upper.
This upper portion of the Expan-
sion Bus address is used to pro-
vide addresses for Flash/EPROM
port accesses.
Read accessible always; write
accessible only when the STOP
bit is set or when SRAM SIZE
(BCR25, bits 7-0) is 0. EPADD-
RU is undefined after H_RESET
and is unaffected by S_RESET or
the STOP bit.
4%&'*0
Bit
Name
Description
31-8
RES
Reserved locations. Written as
zeros and read as undefined.
7-0
EBDATA
Expansion Bus Data Port. EBDA-
TA is the data port for operations
on the Expansion Port involving
Flash accesses.
Flash read cycles are performed
when BCR30 is read. Upon com-
pletion of the read cycle, the 8-bit
result for Flash access is stored
in EBDATA[7:0]. Flash write cy-
cles are performed when BCR30
is written and the FLASH bit
(BCR29, bit 15) is set to 1.
Read and write accessible. EB-
DATA
is
undefined
H_RESET, and is unaffected by
S_RESET and the STOP bit.
after
8!
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15-0
STVAL
Software Timer Value. STVAL
controls the maximum time for
the Software Timer to count be-
fore
generating
(CSR7, bit 11) interrupt. The Soft-
ware Timer is a free-running tim-
er that is started upon the first
write to STVAL. After the first
write, the Software Timer will
continually count and set the
the
STINT
STINT interrupt at the STVAL pe-
riod.
The STVAL value is interpreted
as an unsigned number with a
resolution of 10.24μs. For in-
stance, if STVAL is set to 48,828
(0BEBCh), the Software Timer
period will be 0.5 s.
Setting STVAL to a value of 0 will
result in erratic behavior.
Read
STVAL is set to FFFFh after
H_RESET and is unaffected by
S_RESET and the STOP bit.
and write
accessible.
#
Note:
Bits 15-0 in this register are programmable
through the EEPROM.
Bit
Name
Description
31-16
RES
Reserved locations. Written as
zeros and read as undefined.
15
ANTST
Reserved
tests. Written as 0 and read as
undefined.
for
manufacturing
Note
: Use of this bit will cause
data corruption and erroneous
operation.
Read/Write accessible. ANTST is
set to 0 by H_RESET and is unaf-
fected by S_RESET and the
STOP bit.
14
MIIPD
MII PHY Detect. MIIPD reflects
the quiescent state of the MDIO
pin. MIIPD is continuously updat-
ed whenever there is no manage-
ment operation in progress on the
MII interface. When a manage-
ment operation begins on the in-
terface, the state of MIIPD is
preserved until the operation
ends, when the quiescent state is
again monitored and continuous-
ly updates the MIIPD bit. When
the MDIO pin is at a quiescent
LOW state, MIIPD is cleared to 0.
When the MDIO pin is at a quies-
cent HIGH state, MIIPD is set to
1. Any transition on the MIIPD bit
will set the MIIPDTINT bit (CSR7,
bit 1).