Memory Controller
MPC885 PowerQUICC Family Reference Manual, Rev. 2
15-20
Freescale Semiconductor
15.5.1.1
Chip-Select Assertion Timing
The banks selected by the GPCM support an option to output CS at different timings with respect to the
external address bus. Depending on the value of the ACS field (plus an additional cycle if TRLX = 1), CS
can be output as follows
•
Simultaneous with the external address
•
One quarter of a clock cycle later
•
One half of a clock cycle later
Figure 15-16
shows a basic connection between the MPC885 and an external peripheral device. Here, CS
(the strobe output for the memory access) is connected directly to CE of the memory device and R/W is
connected to the respective R/W in the peripheral device.
1
Read
x
x
00
0
3/4*Clk
x
x
1/4*Clk
x
2+2*SCY
10
1+1/4*Clk 1+3/4*Clk
3+2*SCY
11
1+1/2*Clk
Write
0
00
0
x
3/4*Clk
-1/4*Clk
1/4*Clk
2+2*SCY
10
1+1/4*Clk
1+3/4*Clk
3/4*Clk
3+2*SCY
11
1+1/2*Clk
00
1
00
0
3/4*Clk
-1/4*Clk
1+1/2*Clk
10
1+1/4*Clk
1+3/4*Clk
3/4*Clk
1+1/2*Clk
4+2*SCY
11
1+1/2*Clk
01
00
0
3/4*Clk
-1/4*Clk
1/4*Clk
1+3/8*Clk
3+2*SCY
10
1+1/4*Clk
1+3/4*Clk
3/4*Clk
1+3/8*Clk
4+2*SCY
11
1+1/2*Clk
1
SCY is the number of wait cycles from the option register.
Table 15-11. GPCM Strobe Signal Behavior (continued)
Configuration
Signal Behavior
OR
x
[TRLX]
Access
SCCR
[EBDF]
OR
x
[CSNT]
OR
x
[ACS]
Address
to CS
Asserted
Address
to OE
Asserted
Address
to WE
Asserted
Data to
WE
Asserted
CS
Negated to
Address/
Data Invalid
WE
Negated to
Address/
Data Invalid
Total
Cycles
Summary of Contents for PowerQUICC MPC870
Page 98: ...MPC885 PowerQUICC Family Reference Manual Rev 2 I 4 Freescale Semiconductor ...
Page 118: ...MPC885 Overview MPC885 PowerQUICC Family Reference Manual Rev 2 1 20 Freescale Semiconductor ...
Page 158: ...The MPC8xx Core MPC885 PowerQUICC Family Reference Manual Rev 2 3 18 Freescale Semiconductor ...
Page 288: ...MPC885 PowerQUICC Family Reference Manual Rev 2 III 4 Freescale Semiconductor ...
Page 554: ...MPC885 PowerQUICC Family Reference Manual Rev 2 V 6 Freescale Semiconductor ...
Page 1090: ...UTOPIA Interface MPC885 PowerQUICC Family Reference Manual Rev 2 43 8 Freescale Semiconductor ...
Page 1312: ...Byte Ordering MPC885 PowerQUICC Family Reference Manual Rev 2 A 8 Freescale Semiconductor ...
Page 1336: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 16 Freescale Semiconductor ...
Page 1358: ...MPC885 PowerQUICC Family Reference Manual Rev 2 D 38 Freescale Semiconductor ...
Page 1370: ...MPC880 MPC885 PowerQUICC Family Reference Manual Rev 2 E 4 Freescale Semiconductor ...
Page 1386: ...Revision History MPC885 PowerQUICC Family Reference Manual Rev 2 I 2 Freescale Semiconductor ...