== Usage in CPCs ==
=== Aleste 520EX ===
Used by [[Aleste 520EX]] (a CPC clone with built-in RS232 interface):
EEXXh Aleste - 8251 USART chip (RS232/Mouse) Data (R/W)
EFXXh Aleste - 8251 USART chip (RS232/Mouse) Control/Status (R/W)
Uses a KR580WW51A (russian clone of the 8251).
Clock source comes from a [[8253 chip]].
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=== MHT Ingenieros RS232 para Amstrad ===
Used by RS-232 para Amstrad from MHT Ingenieros, mapped to Ports:
FADCh - MHT RS232 - 8251 USART data
FADDh - MHT RS232 - 8251 USART control/status
Clock source comes from a [[8253 chip]].
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=== Cirkit Serial Interface ===
Used by [[Cirkit serial interface]] (for use with the included Prestel Link modem)):
FADFh - Cirkit - 8251 UART Data register
FBDFh - Cirkit - 8251 UART Status/Control register
TX clock source is fixed (19.2KHz), RX clock source can be selected via DTR bit (1200Hz or 19.2KHz).
== Registers ==
Bit Expl.
0-7 Data
== Usage in CPCs ==
=== Aleste 520EX ===
Used by [[Aleste 520EX]] (a CPC clone with built-in RS232 interface):
EEXXh Aleste - 8251 USART chip (RS232/Mouse) Data (R/W)
EFXXh Aleste - 8251 USART chip (RS232/Mouse) Control/Status (R/W)
Uses a KR580WW51A (russian clone of the 8251).
Clock source comes from a [[8253 chip]].
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=== MHT Ingenieros RS232 para Amstrad ===
Used by [[RS-232 para Amstrad]] from MHT Ingenieros, mapped to Ports:
FADCh - MHT RS232 - 8251 USART data
FADDh - MHT RS232 - 8251 USART control/status
Clock source comes from a [[8253 chip]].
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=== Schneiderware V/24 Interface ===
Used by [[Schneiderware V/24 Interface]] from [[CPC Schneider International]], mapped to Ports:
F9E0h (or F9E2h) Schneiderware V/24 8251 USART chip Data
F9E1h (or F9E3h) Schneiderware V/24 8251 USART chip Control
Clock source comes from a [[8253 chip]].
Clock input to that chip is jumper-selectable: 2MHz (default), or 1MHz
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=== Cirkit Serial Interface ===
Used by [[Cirkit serial interface]] (for use with the included Prestel Link modem)):
FADFh - Cirkit - 8251 UART Data register
FBDFh - Cirkit - 8251 UART Status/Control register
TX clock source is fixed (19.2KHz), RX clock source can be selected via DTR bit (1200Hz or 19.2KHz).
== 8251 vs 8251A ==