Zenith Z-100 PC series Service Manual page 53

Page
5.4
Detailed Circuit Description
Table 5.1 (Continued). 8048/8748 Pin Definitions
DESIGNATION PIN DESCRIPTION
9 Program store enable. This output occurs only during a fetch
to external program memory. (Active low.)
5 Single step input can be used in conjunction with ALE to
"single step" the processor through each instruction. (Active
low.)
EA 7
External access input which forces all program memory
fetches to reference external memory. Useful for emulation
and debug, and essential for testing and program verifica ­
tion. (Active high.)
XTAL1 2 One side of crystal input for internal oscillator.
XTAL2 3 Other side of crystal input.
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