Intel 80C188XL - Manual (Page 173)

CHIP-SELECT UNIT
6-18
6.5 CHIP-SELECTS AND BUS HOLD
The Chip-Select Unit decodes only internally generated address and bus state information. An ex-
ternal bus master cannot make use of the Chip-Select Unit. During HLDA, all chip-selects remain
inactive.
The circuit shown in Figure 6-12 allows an external bus master to access a device during bus
HOLD.
Figure 6-12. Using Chip-Selects During HOLD
6.6 EXAMPLES
The following sections provide examples of programming the Chip-Select Unit to meet the needs
of a particular application. The examples do not go into hardware analysis or design issues.
6.6.1 Example 1: Typical System Configuration
Figure 6-13 illustrates a block diagram of a typical system design with a 128 Kbyte EPROM and
a 32 Kbyte SRAM. The peripherals are mapped to I/O address space. Example 6.1 shows a pro-
gram template for initializing the Chip-Select Unit.
Device select
External Master Chip Select
CSU Chip Select
A1167-0A