Honeywell
COMPONENT MAINTENANCE MANUAL
PART NUMBER 964-0452
I.B.1516A Page 51
Mar 30/01
23-12-01
Assignment of Chip Select Signals
Figure 25
2
EPROM
The control program is permanently programmed in the 2 EPROMs, D7 and 08.
The EPROMs occupy the E0000 to FFFFF memory area, that is to say,
128kByte. The use of 2 EPROMs allows the processor to read out the program
in 16-bit blocks from the EPROMs. Module, D7, is connected to data lines
D0-D7, module, D8 is connected to data lines D8-D15.
3
RAM
RAM is used to store the control data and variables. The read/write memory oc-
cupies the 00000 to 0FFFF memory area. Data can be written in and read out
of the RAMS in 16-bit blocks. Even or odd addresses are selected by control sig-
nals BHE and A0, respectively. Module D10 is connected to data lines PD0 to
PD7, module, D9, to data lines, PD8 to PD15. If the RESET line is on LOW, nei-
ther read nor write operations can be carried out on the RAM.
RAM receives power for at least 5 seconds after the supply voltage has been
disconnected by means of capacitor, C3. Consequently, setting data can be
held in temporary storage in the event of a power failure lasting 5 seconds, and
immediately reset. The power supply is decoupled from the 2 RAMS and the ca-
pacitor by the 2 transistors, V1 and V2, in the event of a voltage collapse.
4
EEPROM
The EEPROM occupies the odd addresses in the memory area from 40000 to
47FFF. Only 8-bit data can be written into and read out of the EEPROM, which
is used to store data that must be retained for more than 5 seconds after power
disconnection. Essentially, this is where the ARINC fault memory is located.
SIGNAL NAME
WRITE
READ
UCS
——
EPROM
LCS
RAM
RAM
MCS0
EEPROM
EEPROM
MCS
1
USART Test Interface
USART Test Interface
MCS2
USART Coupler
USART Coupler
MCS3
——
——
PCS5
Module Bus Data
Module Bus Data
PCS6
Module Bus Control Fault LEDs Parallel Input
PCS0
——
A/D Converter
PCS1
Parallel Output
Parallel Input
PCS2
ARINC BIT Output
ARINC Control Input
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