TOSHIBA SD-2550A
Circuit Diagrams

Table 3-5-4 TMP94C251AF(Z) (1/5)
Pin No. 70 | 77 Name P00~P07 D0~D7 Function Port 0: I/O port Data 0~7: data bus 0~7 Initialized to this function in the external ROM type, TMP94C251A. Becomes high impedance when not accessing to the external memory. Port 1: I/O port Data 8~15: data bus 8~15 Initialized to this function when starting with data bus width higher than 16 bit in the external ROM type, TMP94C251A. Becomes to high impedance when not accessing to the external memory. Port 4: I/O port Address 0~7: address bus 0~7 Initialized to this function in the external ROM type, TMP94C251A. The signal does not change when not accessing to the external memory. Port 5: I/O port Address 8~15: address bus 8~15 Initialized to this function in the external ROM type, TMP94C251A. The signal does not change when not accessing to the external memory. Port 6: I/O port Address 16~23: address bus 16~23 Initialized to this function in the external ROM type, TMP94C251A. The signal does not change when not accessing to the external memory. Port 70: Output port (initialized to �1� output) Read: Strobe signal, which reads the external memory. Develops no strobe signal when not accessing to the external memory. Initialized to this function in the external ROM type, TMP94C251A. Port 71: Output port (initialized to �1� output) Write: Strobe signal, which writes D0 ~ D7 of the external memory. Develops no strobe signal when not accessing to the external memory. Port 72: Output port (initialized to �1� output) Write: Strobe signal, which writes D8 ~ D15 of the external memory. Develops no strobe signal when not accessing to the external memory. Port 73: Output port (initialized to �1� output) Port 74: Output port (initialized to �1� output) Port 75: I/O port Bus request: Signal, which requests to set the memory interface terminal to high impedance. The following terminals become high impedance. But the state does not change while functioning as port. A0~A23, D0~D15, RD, WRLL, WRLH, CS0~CS5, OE0~OE1, WE0~WE1, RAS group, CAS group Port 76: Output port (initialized to �1� output) Bus Acknowledge: Signal, which indicates that BUSRQ request is received. Port 80: Output port (initialized to �1� output) Chip select 0: Develops �L� level when the address is within the assigned address area. 53 Pin No. 59

Table 3-5-4 TMP94C251AF(Z) (2/5)
Name P81 CS1 RAS0 58 P82 CS2 Function Port 81: Output (initialized to �1� output) Chip select 1: Develops �L� level when the address is within the assigned address area. Low address strobe 0: Develops RAS strobe signal for DRAM when the address is within the assigned address area. Port 82: Output port (initialized to �1� output) Chip select 2: Develops �L� level when the address is within the assigned address area. Port 83: Output port (initialized to �1� output) Chip select 3: Develops �L� level when the address is within the assigned address area. Low address strobe 1: Develops RAS strobe signal for DRAM when the address is within the assigned address area. Port 84: Output port (initialized to �1� output) Chip select 4: Develops �L� level when the address is within the assigned address area. Port 85: Output port (initialized to �1� output) Chip select 5: Develops �L� level when the address is within the assigned address area. Port 86: I/O port Wait: Bus wait request signal Port A0: Output port (initialized to �1� output) Column address strobe 0: Develops CAS strobe signal for DRAM when the address is within the assigned address area. Lower column address strobe 0: Develops lower CAS strobe signal for DRAM when the address is within the assigned address area. Port A1: Output port (initialized to �1� output) Upper column address strobe 0: Develops upper CAS strobe signal for DRAM when the address is within the assigned address area. Port A2: Output port (initialized to �1� output) Out enable 0: Develops out enable signal for DRAM. Port A3: Output port (initialized to �1� output) Out enable 1: Develops out enable signal for DRAM. Port A4: Output port (initialized to �1� output) Write enable 0: Develops write enable signal for DRAM. Port B0: Output port (initialized to �1� output) Column address strobe 1: Develops CAS strobe signal for DRAM when the address is within the assigned address area. Lower column address strobe 1: Develops lower CAS strobe signal for DRAM when the address is within the assigned address area. Port B1: Output port (initialized to �1� output) Upper column address strobe 1: Develops upper CAS strobe signal for DRAM when the address is within the assigned address area.

79 | 86

P10~P17 D8~D15

108 P40~P47 | A0~A7 115

57

P83 CS3

RAS1 56 P84 CS4

99 P50~P57 | A8~A15 106

90 | 97

P60~P67 A16~A23

55

P85 CS5

68

P70 RD

29 49

P86 WAIT PA0 CAS0

LCAS0

67

P71 WRL

50

PA1 UCAS0

66

P72 WRH

51

PA2 OE0 PA3 OE1 PA4 WE0 PB0 CAS1

65 64 63

P73 P74 P75 BUSRQ

52

44

62

P76 BUSAK P80 CS0

LCAS1

60

45

PB1 UCAS1

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