Real-Time Clock/Complementary Metal-Oxide Semiconductor Ram; Rt/Cmos Ram Address Map - IBM Personal System/2 50 Technical Reference

Real-Time Clock/Complementary Metal-Oxide
Semiconductor RAM
The real-time clock/complementary metal-oxide semiconductor RAM
(RT/CMOS) chip contains the real-time clock and 64 bytes of CMOS
RAM. The internal clock circuitry uses 14 bytes of this memory, and
the rest is allocated to configuration and system status information.
A 6-Vdc lithium battery maintains voltage to the RT/CMOS RAM when
the power supply is not in operation.
The system cover can be locked to prevent battery removal and loss
of password and configuration information.
The following figure shows the RT/CMOS RAM bytes and their
addresses.
Addre ••
(Hex)
000 - 000
OOE
OOF
010
011
012
013
014
015 - 016
017 - 018
019 - 031
032- 033
034- 036
037
038 -03F
RT/CMOS RAM Byte.
Real-Time Clock Bytes
Diagnostic Status Byte
Shutdown Status Byte
Diskette Drive Type Byte
First Fixed Disk Drive Type Byte
Second Fixed Disk Drive Type Byte
Reserved
Equipment Byte
Low and High Base Memory Bytes
Low and High Expansion Memory Bytes
Reserved
Configuration CRC Bytes
Reserved
Date Century Byte
Reserved
Figure 3-8.
RT/CMOS
RAM Address Map
3-12 Model 50 System Board