Chip Selects
Am186™CC/CH/CU Microcontrollers User’s Manual
5-5
■
To use the Midrange Memory Chip Select (MCS), configure the following options in the
MMCS and MPCS registers:
– Base address (BA[19–13] bit field in MMCS)
– MCS0-Only mode (MCS0_ONLY bit in MMCS)
– External Ready mode (R2 bit in MMCS)
– Wait state value (R1 and R0 bits in MMCS)
– MCS block size (M[6–0] bits in MPCS)
– Memory data bus width for all non-UCS and non-LCS memory (OMSIZ bit in MPCS)
The MCS chip selects are activated after both the MMCS and MPCS registers are written.
Note: To configure the bus width for memory that does not reside in the LCS or UCS chip-
select memory regions, program the OMSIZ bit in the MPCS register. To configure the bus
width for I/O space, program the IOSIZ bit in the MPCS register.
5.5.2
Selecting Memory and I/O Space
All the chip selects can refer to addresses in memory. Only the PCS chip selects can
reference I/O space. Figure 5-2 on page 5-6 shows which part of memory each chip select
can address. The MCS chip selects should not be configured to overlap with memory space
used by UCS, LCS, or PCS. Figure 5-3 on page 5-7 shows the I/O space PCS7–PCS0 can
select.
5.5.2.1
UCS
The Am186CC/CH/CU microcontrollers provide the UCS chip select for the top of the
1-Mbyte memory address space. The upper boundary is FFFFFh; the lower boundary is
programmable with the LB bit field in the UMCS register. The block size must be a multiple
of 64 Kbyte.
5.5.2.2
LCS
The LCS chip select is for the bottom of the 1-Mbyte memory address space. The lower
boundary is 00000h; the upper boundary is programmable with the UB bit field in the LMCS
register. The block size must be a multiple of 64 Kbyte.
5.5.2.3
MCS3–MCS0
MCS3–MCS0 provide for a user-locatable memory block. The base address can reside
anywhere in the 1-Mbyte memory address space as long as the base is an integer multiple
of the block size (0 is a valid multiple), and memory space is not already mapped to by
UCS, LCS (unless they are mapped to DRAM), or PCS.
The Am186CC/CH/CU microcontrollers also offer MCS0 Only mode. When the MCS0-
ONLY bit in the MMCS register is cleared (the default) and the MCS chip selects are enabled,
MCS3–MCS0 are each asserted over one fourth of the total block size. When this bit is set
and the MCS chip selects are enabled, MCS0 is asserted over the entire MCS address
range, and MCS3–MCS1 are still asserted over their individual address ranges. This means
the entire middle chip select range is selectable through MCS0; the remaining MCS pins
are available for other functions. This mode is useful if only one chip select is required or
if DRAM is selected. For more information, see “Selecting DRAM Using the Chip Selects”
on page 5-7.
The BA bit field in the MMCS register programs the base address; the M[6–0] bits in the
MPCS register program the total block size; the MCS0_ONLY bit in the MMCS register
enables MCS0 Only mode.
Summary of Contents for Am186 CC
Page 1: ...Am186 CC CH CU Microcontrollers User s Manual Order 21914B...
Page 4: ...iv Am186 CC CH CU Microcontrollers User s Manual...
Page 18: ...Table of Contents xviii Am186 CC CH CU Microcontrollers User s Manual...
Page 24: ...Introduction xxiv Am186 CC CH CU Microcontrollers User s Manual...
Page 40: ...Architectural Overview 1 16 Am186 CC CH CU Microcontrollers User s Manual...
Page 86: ...System Overview 3 36 Am186 CC CH CU Microcontrollers User s Manual...
Page 92: ...Emulator Support 4 6 Am186 CC CH CU Microcontrollers User s Manual...
Page 112: ...DRAM Controller 6 8 Am186 CC CH CU Microcontrollers User s Manual...
Page 134: ...Interrupts 7 22 Am186 CC CH CU Microcontrollers User s Manual...
Page 186: ...Programmable I O Signals 9 8 Am186 CC CH CU Microcontrollers User s Manual...
Page 200: ...Watchdog Timer 11 6 Am186 CC CH CU Microcontrollers User s Manual...
Page 232: ...Asynchronous Serial Ports UARTs 13 24 Am186 CC CH CU Microcontrollers User s Manual...
Page 242: ...Synchronous Serial Port SSI 14 10 Am186 CC CH CU Microcontrollers User s Manual...
Page 264: ...High Level Data Link Control HDLC 15 22 Am186 CC CH CU Microcontrollers User s Manual...
Page 332: ...Universal Serial Bus USB 18 34 Am186 CC CH CU Microcontrollers User s Manual...
Page 348: ...Register Summary A 16 Am186 CC CH CU Microcontrollers User s Manual...
Page 376: ...Index Index 18 Am186 CC CH CU Microcontrollers User s Manual...