Signal System For The 8255 Block; Signal System For The 8253 Block - Sharp MZ-80B Owner's Manual

48
4.3
Signal system for the
8255
block, the
8253
block and the PIO
block
In this paragraph, the constitutions signal systems for the 8255 block, the 8253 block and the PIO
block - which are responsible for essential roles in the system control -are illustrated.
Before description of each section, below are shown the settings of the 8255, 8253 and PIO in the
input/output ports, and also summarized are the service modes of the port of each controller.
Table 4.2
CPU's
Input/Output port
Controller Service mode of each port
$EO PA output
$El
8255
PB input
$E2
Pc output
$E3 mode control
$E4
Co
mode 2 (16 bit rate generator)
$E5
8253
cl
mode 2 (16 bit rate generator)
$E6 C2
mode 2 ( 16 bit rate generator)
$E7
mode control
$E8
A
output mode 3 (bit control)
$E9
mode control A
Z80A-PIO
$EA
B input mode 3 (bit control)
$EB
mode control B