
4-62
Configuration Registers
Bit 0
functions only if bit 1 is 1. When bit 0 is 0, the parallel-port data-latch output-enable signal
from the élanSC310 microcontroller’s CPU, PPOEN, is forced Low, causing the parallel-
port data-latch to drive the parallel-port data bus. When bit 0 is 1, the PPOEN signal is
controlled by bit 5 of the Parallel Port Control register.
This bit is used to enable the bidirectional control for the parallel port. This bit
4.3.89
Function Enable 2 Register (Index B1h)
Bit 7–6
bits 6 and 7 of this register determine the DRAM mode as shown in Table 4-38 on
page 4-63.
When bit 7 of the Function Enable 3 register at Index B4h is 1, the values of
Bit 4–3
change these bits, first clear bit 6 of the I/O Wait State register at Index 61h, then wait for
the next refresh to occur. Then change the high-speed PLL frequency and return to using
the high-speed PLL.
Do not change these bits while running in the High-Speed PLL mode. To
Table 4-36
Latch and Buffer Logic
PPBIENB
PPISBI
EPPMODE
Mode
0
0
0
Output latch, no system buffer, no input buffer, PP output only
0
0
1
(Invalid combination)
0
1
0
Output latch, system buffer, no input buffer, PP output only
0
1
1
Output latch, system buffer, no input buffer, EPP mode
1
0
0
(Invalid combination)
1
0
1
(Invalid combination)
1
1
0
Output latch, system buffer, input buffer, PP is bidirectional
1
1
1
Output latch, system buffer, input buffer, EPP mode
7
0
Bit
Default
EB_RMMD1 EB_RMMD0
0
(Reserved)
0
HSPLLFQ1
0
HSPLLFQ0
0
XTALUSE
0
(Reserved)
0
0
0
Bit
Name
R/W
Function
7
6
5
4
3
2
EB_RMMD1
EB_RMMD0
R/W
R/W
R/W
R/W
R/W
R/W
RAM mode select bit 0
RAM mode select bit 1
(Reserved—must be 0)
High-speed PLL frequency select, bit 1
High-speed PLL frequency select, bit 0
Crystal interface:
1 = 14.336 MHz out on X1OUT pin
0 = Three-state X1OUT pin (see bit 6 of the Function Enable 1 register at
Index B0h)
(Reserved)
HSPLLFQ1
HSPLLFQ0
XTALUSE
1-0