Intel 80C188XL, 80C186XL user manual Chip-Selectunit

				CHIP-SELECT UNIT
DRAM_BASE	EQU	256	;window start address in Kbytes
DRAM_SIZE	EQU	256	;window	size in Kbytes
DRAM_WAIT	EQU	0	;wait states
DRAM_RDY	EQU	INTRDY	;ignore	bus ready

;The MPCS register is used to program both the MCS and PCS chip-selects. ;Below are the equates for the I/O peripherals (also used to program the PACS ;register.

IO_WAIT	EQU	4	;IO wait states
IO_RDY	EQU	INTRDY	;ignore bus ready
PCS_SPACE	EQU	IO	;put PCS#	chip-selects in I/O space
PCS_FUNC	EQU	ALLPCS	;generate	PCS5# and PCS6#

;The MMCS and MPCS register values are calculated using the above system ;constraints and the equations below:

MMCS_VAL	EQU	(DRAM_BASE SHL	6) OR (001F8H) OR (DRAM_RDY) OR (DRAM_WAIT)
MPCS_VAL	EQU	(DRAM_SIZE SHL	5) OR (08038H) OR (PCS_SPACE) OR (PCS_FUNC) OR
&		(IO_RDY) OR (IO_WAIT)

;I/O is selected using the PCS0# chip-select. Wait states assume operation at ;16 MHz. For this example, the Floppy Disk Controller is connected to PCS2# and ;PCS1# provides the DACK signal.

IO_BASE EQU 1 ;I/O start address in Kbytes

;The PACS register value is calculated using the above system constraints and ;the equation below.

PACS_VAL EQU (IO_BASE SHL 6) OR (0038H) OR (IO_RDY) OR (IO_WAIT)

;The following statements define the default assumptions for segment locations.

	ASSUME	CS:CODE
	ASSUME	DS:DATA
	ASSUME	SS:DATA
	ASSUME	ES:DATA
CODE	SEGMENT PUBLIC 'CODE'
;
;Entry point on power-up
;
FW_START	LABEL	FAR		;forces far jump
	CLI			;disable interrupts
;Place register initialization code here
;
;Set up chip-selects.
;UCS - EPROM Select			(initialized during POWER_ON code)
;LCS - SRAM Select			(set to SRAM size)
;PCS - I/O Select			(PCS1:0 to support floppy)
;MCS - DRAM Select			(set to DRAM size)
	mov	dx, LMCS_REG		;set up LMCS register
	mov	ax, LMCS_VAL
	out	dx, al		;remember that byte writes are OK

Example 6-1. Initializing the Chip-Select Unit (Continued)

6-21