Commodore 128 Programmer's Reference Manual page 638

628 COMMODORE 128
T IM IN G SPECIFICATION
IN TER N A L ROMs
This section specifies timing parameters for both the 23128 and the 27256 Read Only
Memories. This timing spec applies to internal ROMs and for external ROMs run at 1
MHz. For external ROMs run at 2 M Hz, see Table 16-18.
PARAM ETER
Address Valid to Output Delay
Chip Enable to Output Delay
Output Enable to Output Delay
Table 16-17. Internal ROM Timing
R D D R E S 5 -
C H I P
E N A B L E
O U T P U T
E N A B L E
D A T A
Figure 16-25. ROM Timing Diagram
EXTERNAL ROMS
All C64 mode external ROMs and many C l 28 mode external ROMs can be of the type
mentioned above. Any external ROM that is to run at 2 MHz must be faster, as
specified in Table 16-18.
PARAM ETER
Address Valid to Output Delay
Chip Enable to Output Delay
Output Enable to Output Delay
T ab le 16-18. E xtern al 2 M H z RO M T im in g
SYMBOL MIN
300
T
a c c
300
T
c e
120
T
o e
KM
SYMBOL MIN
250
T
a c c
200
T
c e
100
T
oe
MAX UNIT
— ns
— ns
— ns
MAX UNIT
ns
—
ns
—
ns
—