Sharp PC-1211 Service Manual page 8

8
• Input buffer
Remaining 80 bytes (10 memories equivalent) of the display chip 1 is used for the input buffer,
which is used in the following functions:
1. Any information entered through the keyboard is stored once in this buffer, thus allowing up
to 80 steps.
2. The display contents is stored by the CPU I and the CPU II makes selection out of this data.
3. When an arithmetical instruction is entered, its procedure is stored in this buffer by the CPU I
and the CPU II performs operation according to this procedure.
4. When program or reserve program is to be recorded or read out during the execution of the
cassette control instruction, action takes place through this input buffer.
• Transfer buffer
8 bytes (1 memory equivalent) of the display chip 1 is used as a transfer buffer which is used in
the transaction of instruction between the CPU I and the CPU II.
16 bits
----1}4bit
1 memory
• Fixed memory
The total memory of 176 bytes from the display chip 2 and 3 is used as a fixed memories, A-V
(22 memories).
• 8-digit display buffer
40 bytes of 8-digit display buffer is used as a display data buffer during displaying and also used
as a buffer memory for arithmetical result during the arithmetical operation.
128
80 step input buffer
Fixed memories
(L-V, 11 memories)
Fixed memories
(A-K, 11 memories)
Transfer buffer
040
048
8-digit display buffer
8-digit display buffer 8-digit display buffer
000
DISPLAY CHIP 3 DISPLAY CHIP 2
DISPLAY CHIP 1
• Map of the RAM incorporated in the display chip
There are three lK-bit RAMs (128 bytes each) incorporated in each of display chips (SC43125),
having the following configurations: