Intel 8XC251SP User Manual
8XC251SA, SB, SP, SQ USER’S MANUAL
4-6
Figure 4-3. Configuration Byte UCONFIG0
UCONFIG0
(1), (3)
(1), (3)
Address:FF:FFF8H (2)
7
0
UCON
WSA1#
WSA0#
XALE#
RD1
RD0
PAGE#
SRC
Bit
Number
Bit
Mnemonic
Function
7
UCON
87C251Sx
Configuration Byte Location Selector (OTPROM/EPROM products only):
Clearing this bit causes the 8XC251S
x
to fetch configuration information
from on-chip memory. Leaving this bit unprogrammed (logic 1) causes the
8XC251S
8XC251S
x
to fetch configuration information from on-chip memory if EA# =
1 or from external memory if EA# = 0.
—
80C251Sx
83C251Sx
83C251Sx
Reserved:
Write a 1 to this bit when programming UCONFIG0.
6:5
WSA1:0#
Wait State A (all regions except 01:):
For external memory accesses, selects the number of wait states for RD#,
WR#, and PSEN#.
WR#, and PSEN#.
WSA1#
WSA0#
0
0
Inserts 3 wait states for all regions except 01:
0
1
Inserts 2 wait states for all regions except 01:
1
0
Inserts 1 wait state for all regions except 01:
1
1
Zero wait states for all regions except 01:
4
XALE#
Extend ALE:
Set this bit for ALE = T
OSC
.
Clear this bit for ALE = 3T
OSC
(adds one external wait state).
3:2
RD1:0
Memory Signal Selection:
RD1:0 bit codes specify an 18-bit, 17-bit, or 16-bit external address bus and
address ranges for RD#, WR#, and PSEN#. See Table 4-2.
address ranges for RD#, WR#, and PSEN#. See Table 4-2.
1
PAGE#
Page Mode Select:
Clear this bit for page mode enabled with A15:8/D7:0 on P2 and A7:0 on P0.
Set this bit for page mode disabled with A15:8 on P2 and A7:0/D7:0 on P0
(compatible with 44-pin PLCC and 40-pin DIP MCS 51 microcontrollers).
Set this bit for page mode disabled with A15:8 on P2 and A7:0/D7:0 on P0
(compatible with 44-pin PLCC and 40-pin DIP MCS 51 microcontrollers).
0
SRC
Source Mode/Binary Mode Select:
Clear this bit for binary mode (compatible with MCS 51 microcontrollers).
Set this bit for source mode.
Set this bit for source mode.
NOTES:
1.
1.
User configuration bytes UCONFIG0 and UCONFIG1 define the configuration of the 8XC251S
x
.
2.
Address. UCONFIG0 is the second-lowest byte of the 8-byte configuration array. As determined by
UCON and EA#, the 8XC251S
UCON and EA#, the 8XC251S
x
fetches configuration information from on-chip nonvolatile memory at
addresses FF:FFF8H and FF:FFF9H or from external memory using these same addresses. In exter-
nal memory, configuration information is obtained from an 8-byte configuration array located at the
highest addresses implemented. The location of the configuration array in external memory depends
on the size and decode arrangement of the external memory (Table 4-1 and Figure 4-2).
nal memory, configuration information is obtained from an 8-byte configuration array located at the
highest addresses implemented. The location of the configuration array in external memory depends
on the size and decode arrangement of the external memory (Table 4-1 and Figure 4-2).
3.
Instructions for programming and verifying on-chip configuration bytes are given in Chapter 14.