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PCA84C923AP

Microcontrollers for universal infrared remote transmitter applications

Philips Electronics 

Philips Semiconductors

Microcontrollers for universal infrared

remote transmitter applications

Product specification

PCA84C922; PCA84C923

6 GENERAL OPERATION DESCRIPTION

The main application for the PCA84C92X is as a universal

infrared remote control commander and in this role the

PCA84C92X offers the complete solution in one chip.

The PCA84C92X can be programmed to generate code

data that conforms to any protocol (Philips, NEC, RCA,

Thomson and Siemens etc.) and is suitable for use in the

remote control of TVs, VCRs, audio equipment,

air-conditioning systems and in many other applications.

The ability of the PCA84C923D to access external

memory and therefore support more protocols, makes it an

extremely versatile device.

After a Power-on-reset, the scan lines are set LOW and

the sense lines HIGH. If the system has entered the Stop

mode (by software) then when any key is depressed an

external interrupt will be generated and the system will be

woken-up.

If the external interrupt was enabled (by using the ‘EN I’

instruction) before the Stop mode was entered, then when

the CPU is woken-up, the instruction that follows the STOP

instruction will be executed before diverting to the interrupt

routine at vector address 03H. However, if the interrupt

was not enabled before the Stop mode was entered, then

when the CPU is woken-up the instruction that follows the

STOP instruction will be executed.

6.1 System selection

Different systems (TV or VCR etc.) can be controlled using

one universal infrared remote control commander;

switches can be used to select a specific system.

However, the PCA84C92X provides pin T1 for system

selection purposes and software is used to detect the

specific system. Port lines P14 to P17 can also be used for

system selection if their wake-up functions have not been

selected as a mask option.

When no key is pressed the scan lines (Port 0) can be

programmed HIGH and the sense lines (Port 1)

programmed LOW. If a diode is connected between a

sense line and scan line then the scan line will be pulled

LOW and this can be detected by a read operation to

Port 0.

6.2 Key scanning

Port lines P10 to P17 and T0/INT have been designed to

be used as key sense lines. However, if the wake-up

option is not selected for ports P14 to P17 then these can

be used as general I/O lines.

Port lines P00 to P07, P20 to P23 and DP60 to DP67 can

be used as key scan lines or general I/O ports. Derivative

Port 6 also provides the High byte address for the Coding

Table, even when used as scan lines.

6.3 Accessing command code

When any key is depressed its function and operation

protocol are determined, then the command code is read.

If the command code is stored in system ROM it can be

accessed using the ‘MOVP A,@A’ instruction. If the

command code resides in Coding Table ROM it can be

accessed by writing the address to DP60 to DP67 (High

byte) and P00 to P07 (Low byte) and then reading the data

from DP50 to DP57.

In Normal mode, if the Coding Table address is within the

0000 to 1FFFH range for PCA84C922 devices, or within

the 0000 to 3FFFH range for PCA84C923 devices, then

the internal Coding Table will be accessed when

Derivative Port 5 (address 05H) is read.

In the Normal mode only the PCA84C923D has the ability

to access external memory. If the Coding Table address is

greater than 3FFFH then the external memory will be

accessed when Derivative Port 5 (terminal) is read.

When the PCA84C923D is used in the Emulation mode,

when Derivative Port 5 is read, data will always be read

from DP50 to DP57 terminals. Therefore, the internal

Coding Table ROM can be emulated when the

PCA84C923D and the bond-out chip PCF84C00 are used.

1997 Oct 22

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