P R E L I M I N A R Y
PERIPHERAL CONTROL BLOCK
The integrated peripherals of the Am186ED/EDLV mi-
crocontrollers are controlled by 16-bit read/write regis-
ters. The peripheral registers are contained within an
internal 256-byte peripheral control block (PCB). The
registers are physically located in the peripheral de-
vices they control, but they are addressed as a single
256-byte block. Table 8 shows a map of these regis-
ters.
Reading and Writing the PCB
Code written for the Am186ED/EDLV microcontrollers
should perform all writes to the PCB registers as byte
writes. These writes transfer 16 bits of data to the PCB
register even if an 8-bit register is named in the instruc-
tion. For example, out dx, alresults in the value of
axbeing written to the port address in dx. Reads to the
PCB should be done as word reads. Code written in
this manner runs correctly on the Am186ED/EDLV mi-
crocontrollers with the PCB overlayed on either 8- or
16-bit address spaces.
Unaligned reads and writes to the PCB result in unpre-
dictable behavior.
For a complete description of all the registers in the
PCB, see the Am186ED/EDLV Microcontrollers User’s
Manual, order# 21335A.
38
Am186ED/EDLV Microcontrollers
AMD [ AMD ]
