AM186ES Advanced Micro Devices, AM186ES Datasheet - Page 71

• 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

5.1
Table 5-1
CHAPTER
5
CHIP SELECT UNIT
OVERVIEW
The Am186ES and Am188ES microcontrollers contain logic that provides programmable
chip select generation for both memories and peripherals. In addition, the logic can be
programmed to provide ready or wait-state generation and latched address bits A1 and A2.
The chip select lines are active for all memory and I/O cycles in their programmed areas,
whether they are generated by the CPU or by the integrated DMA unit.
The Am186ES and Am188ES microcontrollers provide six chip select outputs for use with
memory devices and six more for use with peripherals in either memory space or I/O space.
The six memory chip selects can be used to address three memory ranges. Each peripheral
chip select addresses a 256-byte block offset from a programmable base address (see
Section 4.1.1 on page 4-3).
The chip selects are programmed through the use of five 16-bit peripheral registers (Table
5-1). The UMCS register, offset A0h, is used to program the Upper Memory Chip Select
(UCS). The LMCS register, offset A2h, is used to program the Lower Memory Chip Select
(LCS). The Midrange Memory Chip Selects (MCS3–MCS0) are programmed through the
use of two registers—the MMCS register, offset A6h and the MPCS register, offset A8h.
In addition to its use in configuring the MCS chip selects, the MPCS register and the PACS
register are used to program the Peripheral Chip Selects (PCS6–PCS5 and PCS3–PCS0).
Note: The SYSCON register contains the MCSBIT field which determines behavior of the
MCS0 chip select. The PCS4 chip select is not implemented on the Am186ES and
Am188ES microcontrollers.
Chip Select Register Summary
Offset
A0h
A2h
A4h
A6h
A8h
Register
Mnemonic
UMCS
LMCS
PACS
MMCS
MPCS
Register Name
Upper Memory Chip Select
Lower Memory Chip Select
Peripheral Chip Select
Midrange Chip Select
PCS and MCS Auxiliary
Chip Select Unit
Affected Pins Comments
UCS
LCS
PCS6–PCS5
PCS3–PCS0
MCS3–MCS0
PCS6–PCS5
PCS3–PCS0
MCS3–MCS0
Ending address is fixed at
FFFFFh
Starting address is fixed at
00000h
Block size is fixed at 256
bytes
Starting address and block
size are programmable
Affects both PCS and MCS
chip selects
5-1