Bit Settings For Mccr2—0Xf4 - Motorola MPC8240 User Manual

Memory Control Configuration Registers
Bits Name
31–29 TS_WAIT_
TIMER[0–2]
28–25 ASRISE[0–3]
24–21 ASFALL[0–3]
4-46
Table 4-39. Bit Settings for MCCR2—0xF4
Reset
Value
000 Transaction start wait states timer. The minimum time allowed for ROM/Flash/Port
X devices to enter high impedance is 2 memory system clocks.
TS_WAIT_TIMER[0–2] adds wait states before the subsequent transaction starts in
order to account for longer disable times of a ROM/Flash/Port X device. This delay
is enforced after all ROM and Flash accesses, delaying the next memory access
from starting (for example, DRAM after ROM access, SDRAM after Flash access,
ROM after Flash access).
Note that this parameter is supported for SDRAM systems only. For EDO/FPM
DRAM systems, TS_WAIT_TIMER[0–2] must = 000.
Bits
Reads with
wide data path
(32 or 64-bit)
000 2 clocks
001 2 clocks
010 3 clocks
100 5 clocks
101 6 clocks
111 8 clocks
Note 1. In this context, Flash writes are defined as any write to RCS0 or
RCS1.
Note 2: For Flash writes, add the write recovery time, ROMNAL, to the
given wait states for ROM high-impedance time.
0000 AS rise time. These bits control the rising edge timing of the AS signal for the Port X
interface. See Section 6.4.7, "Port X Interface," for more information.
0000 Disables AS signal generation
0001 1 clock
0010 2 clocks
0011 3 clocks
...
1111 15 clocks
0000 AS fall time. These bits control the falling edge timing of the AS signal for the Port X
interface. See Section 6.4.7, "Port X Interface," for more information.
0000 0 clocks (AS asserted coincident with the chip select)
0001 1 clock
0010 2 clocks
0011 3 clocks
...
1111 15 clocks
MPC8240 Integrated Processor User's Manual
Description
Wait States for ROM High Impedance
Reads with gather
data path in
flow-through or
registered buffer
mode (8, 16, 32-bit)
5 clocks
5 clocks
5 clocks
6 clocks
7 clocks
9 clocks
1, 2
All writes and reads
with gather data path
in in-line buffer mode
(8, 16, 32,-bit)
6 clocks
6 clocks
6 clocks
7 clocks
8 clocks
10 clocks