PCA84C922AP PHILIPS [NXP Semiconductors], PCA84C922AP Datasheet - Page 18

• Manufacturer Part Number: PCA84C922AP
• Description: Microcontrollers for universal infrared remote transmitter applications
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
8
The code data transmitted from the LOUT output when any
key is depressed, is stored in a memory area known as the
Coding Table. The PCA84C92X range of microcontrollers
have on-chip ROM specifically for this use (system ROM
may also be used). The Coding Table is addressed via
Port 0 (the Low byte address) and Derivative Port 6 latch
(the High byte address).
The PCA84C922 range of devices have 8 kbytes of ROM
for use as a Coding Table and when accessing this internal
memory, address lines DP65 to DP67 must be LOW.
The PCA84C923 range of devices have 16 kbytes of ROM
for use as a Coding Table and when accessing this internal
memory, address lines DP66 and DP67 must be LOW.
The Coding Table memory size for the PCA84C923D
however, can be extended up to 64 kbytes by adding
external memory (ROM or EPROM). The external memory
data bus is connected to Derivative Port 5. Accessing the
internal or external Coding Tables of the PCA84C923D is
described below.
Table 7 Subroutine to access the Coding Table
1997 Oct 22
CODE
CODE1
CODE2
ADDRESS
In the Normal mode (EMU pin LOW)
– When Derivative Port 5 terminal is read, if the
– When Derivative Port 5 terminal is read, if either of
Microcontrollers for universal infrared
remote transmitter applications
CODING TABLE
address lines DP66 and DP67 are LOW, the address
will be within the internal memory boundary, and the
internal Coding Table will be accessed.
the address lines DP66 or DP67 is HIGH, the address
will be outside the internal memory boundary and the
external memory will be accessed. The data at
Derivative Port 5 terminal will then be read.
ORL P1,#FF
MOV A,R4
MOV D8,A
MOV A,R3
OUTL P0,A
MOV A,D5
MOV @R0,A
DJNZ R1,CODE2
RET
INC R0
INC R3
JMP CODE1
INSTRUCTION
Set all sense lines to logic 1.
Load Accumulator with the High byte of the starting address.
Write the High byte of the starting address to Derivative Port 6 latch.
Load Accumulator with the Low byte of the starting address.
Write the Low byte of the starting address to Port 0.
Read code data from Derivative Port 5 terminal into the Accumulator.
Store code data in system RAM.
If more code data is to be read jump to CODE 2, if not go to next instruction.
Return from subroutine to main program.
Increment RAM address pointer.
Increment Low byte address of Coding Table.
Jump to CODE 1.
18
8.1
The procedure for accessing the Coding Table follows:
1. Set all sense lines to a logic 1.
2. Write the High byte address to Derivative Register 08
3. Write the Low byte address to Port 0 (Low byte
4. Read Derivative Register 05 (Derivative Port 5
5. Repeat steps 4 and 5 to read more code data.
Table 7 shows a subroutine that reads the Coding Table
and then loads code data into system RAM.
Entry:
Exit:
In the Emulation mode (EMU pin HIGH)
– When Derivative Port 5 terminal is read, external
R0 contains the starting address in system RAM into
which data will be loaded.
R1 contains the number of bytes in the Coding Table
which are to be read.
R3 holds the Coding Table starting address (Low byte).
R4 holds the Coding Table starting address (High byte).
((R0)), ((R0) + 1)
data
(Derivative Port 6 latch).
address latch of internal Coding Table).
terminal); code data has now been retrieved.
memory will always be accessed. In this situation,
Derivative Port 5 latch cannot be read.
Accessing the Coding Table
DESCRIPTION
PCA84C922; PCA84C923
((R0) + (R1)
Product specification
1) contain the code