AM186ES Advanced Micro Devices, AM186ES Datasheet - Page 80

• Manufacturer Part Number: AM186ES
• Description: microcontrollers provide a low-cost/ high-performance solution for embedded system designers who wish to use the x86 architecture.
• Manufacturer: Advanced Micro Devices

5.5.4
Figure 5-4
Table 5-4
5-10
PCS and MCS Auxiliary Register
(MPCS, Offset A8h)
The PCS and MCS Auxiliary (MPCS) register (see Figure 5-4) differs from the other chip
select control registers in that it contains fields that pertain to more than one type of chip
select. The MPCS register fields provide program information for MCS3–MCS0 as well as
PCS6–PCS5 and PCS3–PCS0.
In addition to its function as a chip select control register, the MPCS register contains a
field that configures the PCS6–PCS5 pins as either chip selects or as alternate sources for
the A2 and A1 address bits. When programmed to provide address bits A1 and A2, PCS6–
PCS5 cannot be used as peripheral chip selects. These outputs can be used to provide
latched address bits for A2 and A1.
On reset, PCS6–PCS5 are not active. If PCS6–PCS5 are configured as address pins, an
access to the MPCS register causes the pins to activate. No corresponding access to the
PACS register is required to activate the PCS6–PCS5 pins as addresses.
PCS and MCS Auxiliary Register
The value of the MPCS register at reset is undefined.
Bit 15: Reserved—Set to 1.
Bits 14–8: MCS Block Size (M6–M0)—This field determines the total block size for the
MCS3–MCS0 chip selects. Each individual chip select is active for one quarter of the total
block size. The size of the memory block defined is shown in Table 5-4.
Only one of the bits M6–M0 can be set at any time. If more than one of the M6–M0 bits is
set, unpredictable operation of the MCS lines occurs.
If the MCSBIT in the SYSCON register is set, MCS0 asserts over the entire programmed
block size. MCS3–MCS1 will continue to assert over their programmed range but are
typically used as PIOs in the configuration.
MCS Block Size Programming
Total Block
128K
256K
512K
Size
16K
32K
64K
8K
Select Size
Individual
15
1
128K
16K
32K
64K
2K
4K
8K
M6–M0
Chip Select Unit
0000001b
0000010b
0000100b
0001000b
0010000b
0100000b
1000000b
M6–M0
EX
7
MS
1 1 1
R2
R1–R0
0