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PCA84C923CT Datasheet(PDF) 10 Page - NXP Semiconductors |
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PCA84C923CT Datasheet(HTML) 10 Page - NXP Semiconductors |
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10 / 36 page  1997 Oct 22 10 Philips Semiconductors Product specification Microcontrollers for universal infrared remote transmitter applications 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. 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. 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. 6.3 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. |
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