Download local

MC2 Functions
where BCK is the value programmed in the Bus Clock
register, and BUS CLOCK is the MC68xx0x0 bus clock
frequency.
3
EPROM Access Time Control Register
The MVME1X2P4 is populated with a 150ns EPROM memory device.
Due to the wide range of EPROM speeds, the contents can be changed by
software to adjust for a specific speed.
ADR/SIZ
BIT
$FFF42040 (8 bits)
23
22
21
NAME
20
19
ROM0
18
17
16
ET2
ET1
ET0
OPER
R
R
R
R/W
R
R/W
R/W
R/W
RESET
0
0
0
1 PL
0
1 PL
1 PL
1 PL
ET2-ET0 EPROM access time is controlled by the state of ET2ET0. The following table defines the ET2-ET0 encoding
(note that for the MVME1X2P4, whose bus frequency is
1
/2 the processor frequency, only the 33MHz column
applies).
ET2ET0
EPROM Access <= N
at 25MHz where N =
EPROM Access <= N
at 33MHz where N =
$0
60 ns
40 ns
$1
100 ns
70 ns
$2
140 ns
100 ns
$3
180 ns
130 ns
$4
220 ns
160 ns
$5
260 ns
190 ns
$6
300 ns
210 ns
$7
340 ns
240 ns
ROM0
3-38
Refer to the table on the Local Bus Memory Map, Note 1,
in Chapter 1.
Computer Group Literature Center Web Site